==Sen. Tom Carper (D) easily surmounted a primary challenge from the left on September 6, 65%-35%.
==State Rep. Geoff Diehl (R), who billed himself as a strong Trump supporter, easily won the Massachusetts Republican primary to face Sen. Elizabeth Warren. He is a distinct underdog.
==In Arizona, Rep. Kyrsten Sinema (D) handily won the Democratic primary with 81% of the vote and Rep. Martha McSally (R) beat back two more conservative opponents and won going away with 53% on August 28. This is a toss-up race.
==Sen. Tammy Baldwin (D) finally knows who her November opponent is, state senator Leah Vukmir, who survived a bitter battle in the Republican primary 49%-43% between two candidates fighting over who was more loyal to President Trump.
==Sen. Tina Smith (D), appointed to the Senate earlier this year, easily survived a primary with 76% of the vote against a Republican-turned-Democrat and now faces State senator Karin Housley (R), who captured the GOP nomination with 62%.
== Former Libertarian presidential candidate and former Governor Gary Johnson announced he is running for Senate as a third party candidate against New Mexico Senator Martin Heinrich (D).
==Businessman and war vet John James (R) won the GOP nomination on August 7 to face Sen. Debbie Stabenow (D). A Marist poll at the end of July gave Stabenow a strong lead over James, 55% to 37%.
==In Missouri, to no one’s surprise, Sen. Clair McCaskill (D) easily and Josh Hawley (R), the state Attorney General and a little less easily, won their parties’ nominations on August 7.
After the 2016 elections, Democrats picked up two Senate seats, but Republicans maintained a majority of 52 Republicans seats compared to 48 Democratic seats — until the December 12 special election in Alabama to replace Attorney General Jeff Sessions. The partisan breakdown is now 51-49 in favor of the GOP after Doug Jones (D) upset victory in Alabama.
In 2018, the numbers clearly work for the Republicans in Senate elections to retain and even expand their majority. There are 26 Democratic (including two independents) seats up for election and only nine for the Republicans.
The majority of the nine Republican seats look safe for the incumbents. The three major exceptions are Sen. Dean Heller (R) of Nevada, the seat currently held by Sen. Jeff Flake (R) of Arizona and the seat currently held by Sen. Bob Corker (R).
A number of the Democrats have to campaign in states that went for Donald Trump in 2016. Democratic Senators running in states carried by President Trump by double digits include Joe Donnelly in Indiana, Claire McCaskill in Missouri, Jon Tester in Montana, Heidi Heitkamp in North Dakota and Joe Manchin in West Virginia.
On the other hand, mid-term elections can be hard on the party in power, which almost always loses seats. These elections tend to be a referendum on incumbent president; as Donald Trump has proved divisive and controversial in office, there should be openings for Democrats.
Another thought worth considering is that only three incumbent Senators, Bob Corker of Tennessee, Jeff Flake of Arizona and Orrin Hatch of Utah, have announced retirement. However, two Senators resigned their seats, Al Franken of Minnesota and Thad Cochran of Mississippi, creating two special elections this fall. Alt right leader Steve Bannon, later banished from the Trump kingdom, promised other primaries against Republican incumbents, but that threat has petered out.
Ironically, the problems with the Trump administration and the mid-term tendency to go against the party in charge of the White House provides Democrats a better opportunity to win control of the House rather than the Senate where the current margin is much closer, however. Even that calculation may change.
Senators up for re-election in 2018
Democratic seats (26)
California – Dianne Feinstein (D)
Connecticut – Chris Murphy (D)
Delaware – Tom Carper (D)
Florida – Bill Nelson (D)
Hawaii – Mazie Hirono (D)
Indiana – Joe Donnelly (D)
Maine – Angus King (I)
Maryland – Ben Cardin (D)
Massachusetts – Elizabeth Warren (D)
Michigan – Debbie Stabenow (D)
Minnesota A – Amy Klobuchar (D)
Minnesota B – Tina Smith (D)
Missouri – Claire McCaskill (D)
Montana – Jon Tester (D)
New Jersey – Bob Menendez (D)
New Mexico – Martin Heinrich (D)
New York – Kirsten Gillibrand (D)
North Dakota – Heidi Heitkamp (D)
Ohio – Sherrod Brown (D)
Pennsylvania – Bob Casey, Jr. (D)
Rhode Island – Sheldon Whitehouse (D)
Vermont – Bernie Sanders (I)
Virginia – Tim Kaine (D)
Washington – Maria Cantwell (D)
West Virginia – Joe Manchin (D)
Wisconsin – Tammy Baldwin (D)
Republican seats (9)
Arizona – Jeff Flake (R) – retiring
Mississippi A – Roger Wicker (R)
Mississippi B – Cindy Hyde-Smith (R)
Nebraska – Deb Fischer (R)
Nevada – Dean Heller (R)
Tennessee – Bob Corker (R) – retiring
Texas – Ted Cruz (R)
Utah – Orrin Hatch (R) – retiring
Wyoming – John Barrasso (R)
A look at specific 2018 races
Alabama: In the December 12 special election, former U.S. Attorney Doug Jones upset former State Supreme Court Justice Roy Moore (R) in a major upset. Moore was handicapped by charges of harassment of underage teenagers. Jones will serve until 2020.
Arizona: Sen. Jeff Flake (R) has been an ardent and vocal opponent of Donald Trump, and wrote a book detailing his criticisms. On October 24, 2017, in terrible political shape, he announced he would not run again. On August 28, Rep. Kyrsten Sinema (D) easily won the Democratic primary with 81% of the vote and Rep. Martha McSally (R) beat back two more conservative opponents and won going away with 53%. It is a toss-up race.
California: Senator Dianne Feinstein (D) announced in October 2017 that she will run for re-election. On June 5, Feinstein (D) easily outpaced state senate leader Kevin De León for the Democratic nomination 44%-11%, but they face off again in November. De León has been endorsed by the California Democratic Party.
Delaware: Senator Tom Carper (D) is strongly favored, and on September 6, he easily surmounted — 65%-35% — a challenge from the left in the Democratic primary by Dover activist Kerri Evelyn Harris.
Florida: In April 2018, Governor Rick Scott (R) announced his challenge to Senator Bill Nelson (D) in what will be a very expensive and competitive race. Nelson, who is 74, is the most popular politician in Florida, but Scott has won the governorship twice and is very wealthy. Polls show a close contest.
Hawaii: Sen. Mazie Hirono (D) is the overwhelming favorite against Ron Curtis (R), a retired computer engineer who won the August 11 primary.
Indiana: State Rep. Mike Braun (R) defeated two House candidates after a nasty and bitter primary and faces Sen. Joe Donnelly (D). It is a tough state for a Democrat to win.
Maine: Sen. Angus King (I) is in good political shape. He has one Republican opponent, State Sen. Eric Brakey, who is not well known, and one Democratic opponent, Zak Ringelstein, a teacher and a founder of an education business.
Maryland: Incumbent Sen. Ben Cardin (D) is the overwhelming favorite to win re-election in strongly Democratic Maryland. He easily beat back a primary challenge from Chelsea Manning.
Massachusetts: Senator Elizabeth Warren (D) is a very strong candidate. State Rep. Geoff Diehl (R), who billed himself as a strong Trump supporter, easily won the Republican primary in early September.
Michigan: Debbie Stabenow (D) looks to be in strong shape for re-election, but Republican see an opening. Businessman John James (R), who served with the Army in Iraq, won the August 7 primary to face her.
Minnesota (A): In early August, 2017, State Rep. Jim Newberger (R) announced he will challenge Sen. Amy Klobuchar (D), who is the overwhelming favorite.
Minnesota (B): With the departure of Sen. Al Franken (D-MN), accused of sexual transgressions, Governor Mark Dayton appointed his Lieutenant Governor, Tina Smith, as Franken’s replacement. On August 14, Smith easily turned back former George W. Bush White House ethics lawyer Richard Painter, 76%-14%. State Sen. Karin Housley won the Republican nomination.
Mississippi A: Roger Wicker (R) is running for re-election in an overwhelmingly Republican state. He is coasting to re-election after State senator Chris McDaniel (R) dropped his challenge to Wicker to run for the other Mississippi Senate seat. He faces state representative David Baria.
Mississippi B: On March 21, Mississippi Gov. Phil Bryant announced the appointment of Cindy Hyde-Smith, the state’s Commissioner of Agriculture and Commerce, to fill the seat of GOP U.S. Sen. Thad Cochran, who resigned from the Senate on April 1 because of ill-health. State senator Chris McDaniel (R) has dropped his challenge to incumbent Senator Roger Wicker (R) and instead is running for this seat. Former U.S. Representative and Secretary of Agriculture Mike Espy (D) has also entered the race. A post-November 6 runoff is likely.
Missouri: In 2012, Sen. Claire McCaskill (D) was fortunate to run against Rep. Todd Akin (R), who made infamous comments about “legitimate rape.” Attorney General Josh Hawley (R) is the Republican nominee. McCaskill may be the most vulnerable incumbent Senate Democratic candidate.
Montana: Sen. John Tester (D) dodged a bullet when Rep. Ryan Zinke (R), who represented the entire state in the House, was appointed Interior Secretary. But Trump carried the state by 20%, so Tester’s re-election will not be easy. State Auditor Matt Rosendale (R) narrowly won the June 5 GOP primary.
Nebraska: Lincoln City Councilmember Jane Raybould (D), who runs the grocery business her father started more than 53 years ago, is challenging Sen. Deb Fischer (R) in a very tough state for Democrats.
Nevada: Senator Dean Heller (R) is up for election in a state carried twice by President Obama and once by Hillary Clinton. Still, Heller has won four elections in the state and he will not be easy to dislodge. In July 2017, Rep. Jacky Rosen (D) announced she will run. It will be a close election.
New Jersey: Senator Robert Menendez (D) went on trial on federal corruption charges in September, but a hung jury ended the trial. In January 2018, the Justice Department dropped all charges. Bob Hugin (R), formerly a top executive at the pharmaceutical company Celgene, won the June 5 GOP primary to face Menendez, who lost 38% of the Democratic primary vote to an underfunded challenger. There is some concern that Menendez is vulnerable.
New Mexico: Senator Martin Heinrich (D) has a challenger after Albuquerque construction company owner Mark Rich (R) announced his candidacy. Rich has never run for office, but could self-fund. Former Libertarian presidential candidate and former Governor Gary Johnson announced he is running for Senate as a third party candidate.
North Dakota: Sen. Heidi Heitkamp (D) faces an electorate that strongly backed President Trump. In August 2017, state Sen. Tom Campbell (R) entered the race. U.S. Rep. Kevin Cramer (R) first announced he would not run, but in February 2018 reversed course. Campbell promptly dropped out. It’s a toss up.
Ohio: Sen. Sherrod Brown (D) beat back a challenge in 2012 from state treasurer Josh Mandel (R), but in early January 2018, Mandel dropped out of the expected rematch due to his wife’s health problems. After Mandel left the race, U.S. Rep. Jim Renacci (R) switched from running for governor to enter this Senate contest and won the May 8 primary. Brown is favored.
Pennsylvania: Sen. Bob Casey (D) is in a good position to be re-elected, but the state went for Trump in 2016, leaving some uncertainty. In August 2017, Republican Rep. Lou Barletta announced that he will run, and won the May 15 GOP primary.
Tennessee: Sen. Bob Corker (R) has announced his retirement at the end of this term. In December, former Gov. Phil Bredesen (D) entered the Democratic primary. GOP Rep. Marsha Blackburn will be the Republican nominee. Bredesen remains popular, and has a narrow lead.
Texas: U.S. Rep. Beto O’Rourke (D), a three-term Representative from El Paso, is challenging incumbent Sen. Ted Cruz (R). O’Rourke, who is the underdog, is a businessman in the technology industry and a musician who played in three punk rock bands during and after his college years at Columbia University. O’Rourke is raising huge amounts of money in an unconventional campaign and has closed the margin.
Utah: Sen. Orrin Hatch (R) will retire after eight terms in office. Former Republican presidential candidate Mitt Romney (R) is the overwhelming favorite to be elected. He easily brushed back a primary challenge.
Virginia: Prince William County Supervisor Corey Stewart (R), who came close to claiming the Virginia GOP nomination for governor, won the primary on June 12 to face Sen. Tim Kaine (D). In his announcement, Stewart promised to “run a very vicious and ruthless campaign against Tim Kaine and I’m going to win.” Kaine is the overwhelming favorite.
Washington: Sen. Maria Cantwell (D) should have no problem getting re-elected. She faces former TV news anchor and reporter Susan Hutchison.
West Virginia: State Attorney General Patrick Morrisey (R) won the May 8 primary, turning back former Massey Energy CEO Don Blankenship and a third candidate, and faces Sen. Joe Manchin (D) in November. West Virginia is a state which has turned very Republican in recent years but still elects Democrats to the U.S. Senate and as Governor. Blankenship is threatening to run as an independent in the fall.
Wisconsin: While a lot of Republicans circled around the Senate seat of Sen. Tammy Baldwin (D), in the end state Sen. Leah Vukmir (R) won her party’s primary August 14 primary 49%-43% over Marine veteran and businessman Kevin Nicholson (R). Sen. Tammy Baldwin (R) is favored, although conservative groups are spending heavily to defeat her.
Wyoming: Sen. John Barrasso is seeking re-election. Businessman Gary Trauner (D), who very narrowly lost a 2006 House bid, is running against Barrasso.