The midterms have three major parts to look at: the House, the Senate, and gubernatorial races. Summing up 435 House races means there’s no room to devote space to any particular race, but analyzing only 35 Senate races means there is some room for interpretation. Some of the descriptions below may repeat some information, but it’s good to have everything to do with the Senate in one place. In 2018, there are 33 Class I Senate seats up for election, but there are also special elections for Class II seats in Minnesota and Mississippi. Including the two special elections, there are 26 Democratic senators up for election and 9 Republican senators.
Group I: Safe Democratic-held Seats (14)
California: Sen. Dianne Feinstein (D-CA) has been elected senator five times, at first to a two-year special term in 1992 and then to four full-length terms starting in 1994. At 85, she’s the oldest senator. Thanks to California’s top-two primary system, former state senate president Kevin de Léon came in second place in June. He has the state party’s endorsement and is running to Feinstein’s left, but is unlikely to pull off an upset.
Connecticut: Sen. Chris Murphy (D-CT) has only been elected once before, in 2012. He’s running against Republican Matthew Corey, but since he hasn’t done anything to annoy his supporters, there’s nothing to see here.
Delaware: Sen. Tom Carper (D-DE) is running for a fourth term. He and fellow Sen. Chris Coons (D-DE) try very hard to follow in the institutional tradition of working across the aisle, but he also knows when he’s wanted in the “resistance.” His opponent is Republican Rob Arlett.
Hawaii: Sen. Mazie Hirono (D-HI) is running for a second term. She just underwent treatment for kidney cancer, but recovered and stayed in the race. She’s running against Republican Ron Curtis in theory, but the Republican Party of Hawaii is a joke and that hardly matters.
Maine: Sen. Angus King (I-ME) is running for a second term. King is one of two independents who caucuses with the Democrats. He’s done enough to placate Democrats that they didn’t nominate a serious challenger. His main opponent is Republican state senator Eric Brakey.
Maryland: Sen. Ben Cardin (D-MD) is running for a third term. Cardin is noncontroversial and has no notable scandals or baggage, so nothing will stop him from winning. He’s running against former “Republican for Obama” Tony Campbell.
Massachusetts: Sen. Elizabeth Warren (D-MA) is running for a second term. Warren has become one of the most outspoken senators in the country and is both a leader of the progressive movement and a creator of the Consumer Financial Protection Bureau. Her opponent is state representative Geoff Diehl.
Minnesota: Sen. Amy Klobuchar (D-MN) is running for a third term. Klobuchar is the most popular politician in Minnesota, and thus will win by a double-digit margin. By her polling numbers, she’ll win large numbers of Obama-Trump voters that couldn’t bring themselves to vote for Hillary Clinton. Her opponent is state representative Jim Newberger.
New Mexico: Sen. Martin Heinrich (D-NM) is running for a second term. Heinrich is not the most outspoken member of the Democratic caucus, but he suits his state. He’s running against Republican Mark Rich as well as former two-term governor and Libertarian Gary Johnson.
New York: Sen. Kirsten Gillibrand (D-NY) was first appointed in 2009 to replace Hillary Clinton after her nomination as Secretary of State, then won a special election in 2010 and a regular election in 2012. She’s running for a second full term. She’s raised her profile dramatically as one of the senators to vote against the Trump administration more often than almost any other. Her opponent is Republican and Conservative Chele Farley.
Rhode Island: Sen. Sheldon Whitehouse (D-RI) is running for a third term. His prosecutorial prowess was on display at the Brett Kavanaugh and other Senate hearings, endearing him further to supporters. His opponent is Republican former state Supreme Court justice Robert Flanders.
Vermont: Sen. Bernie Sanders (I-VT) is running for a third term. Subsequent to his presidential run, Sanders has cemented his status as the most popular politician in the country among his own constituents. He won and declined the Democratic nomination, so his only opponent is Republican Lawrence Zupan.
Virginia: Sen. Tim Kaine (D-VA) is running for a second term. Kaine is best known as Hillary Clinton’s 2016 running mate, but has still compared a fairly moderate voting record, at least compared to other Senate Democrats. He’s running against Prince William County Supervisor Corey Stewart, who lost the Republican gubernatorial nomination in 2017.
Washington: Sen. Maria Cantwell (D-WA) is running for a fourth term. Her voting record is about what’s expected, given the partisan lean of the state. No surprises here. Her opponent is former state Republican Party chair Susan Hutchison.
Group II: Competitive Democratic-held Seats (12)
Florida: Sen. Bill Nelson (D-FL) is running for a fourth term. He’s currently the only statewide elected Democrat in Florida, and since term-limited Gov. Rick Scott (R-FL) is his opponent, he has his work cut out for him. He’s more likely to win that not, but this should be the smallest margin he’s ever won a race by.
Indiana: Sen. Joe Donnelly (D-IN) is running for a second term. Donnelly is arguably only a senator because his 2012 opponent made a gaffe about rape being part of God’s plan. Polls have shown the race to be close, but Donnelly may have an edge over former state rep. Mike Braun.
Michigan: Sen. Debbie Stabenow (D-MI) is running for a fourth term. Stabenow is only slightly vulnerable due to President Trump’s 2016 victory in Michigan. The state looks likely to swing back hard towards Democrats. Stabenow is running against Republican John James.
Minnesota special: Sen. Tina Smith (D-MN) is running for the final two years of Al Franken’s term. Because appointed incumbents have little advantage, and Minnesota is still competitive in statewide races, Smith’s margin may not exceed that of the national popular vote by much. She’s running against former Republican state senator Karin Housley.
Missouri: Sen. Claire McCaskill (D-MO) is running for a third term. She’s the only Democrat elected statewide left, and if Missourians consolidate their senatorial views with their presidential views, she too will be swept out of office. Her opponent is Republican state attorney general Josh Hawley, who’s attempting to use his current office as a stepping-stone.
Montana: Sen. Jon Tester (D-MT) is running for a third term. Tester’s personal popularity must overcome his state’s partisan lean if he is to win election once again. The fact that state auditor Matt Rosendale (R) is originally from Maryland should help that. Tester has maintained a single-digit lead in polls, just about outside the margin of error.
New Jersey: Sen. Bob Menendez (D-NJ) was originally appointed to the Senate to fill the seat of Jon Corzine (D-NJ), who had been elected governor. He’s running for a third full term, and his seat is only vulnerable to Republican Bob Hugin because of a hung jury on federal corruption charges. He’ll probably win, but may be asked to retire after this election.
North Dakota: Sen. Heidi Heitkamp (D-ND) is running for a second term. She’s definitely built a personal brand in her state, but especially after her vote against Brett Kavanaugh, North Dakota’s fundamental red tint is probably too much to overcome. US Rep. Kevin Cramer (R-ND-AL) is hoping to make this seat a Republican pickup.
Ohio: Sen. Sherrod Brown (D-OH) is running for a third term. He’s supposed to be vulnerable due to President Trump’s 2016 victory here, but it’s not showing against US Rep. Jim Renacci (R-OH-16). This race is only in this group out of an abundance of caution after the preferred Republican nominee, state treasurer Josh Mandel, dropped out. Brown may win by double digits.
Pennsylvania: Sen. Bob Casey (D-PA) is running for a third term. He’s up over US Rep. Lou Barletta (R-PA-11) by double digits in all but one recent poll. Once again, this race is only in this group due to President Trump’s 2016 victory here, and Casey should win, by a lot.
West Virginia: Sen. Joe Manchin (D-WV) was first elected in a special election in 2010 to replace Sen. Robert Byrd. After election to a full term in 2012, he’s running for a second full term. A combination of his voting record, personal popularity, and vote for Brett Kavanaugh seem to have kept his seat in Democratic hands.
Wisconsin: Sen. Tammy Baldwin (D-WI) is running for a second term. Like Sens. Casey, Brown, and Stabenow, she was thought to be vulnerable at the beginning of the election cycle because of results from the 2016 election, but polls have banished that thought. Her opponent is Republican state senator Leah Vukmir.
Group III: Competitive Republican-held Seats (5)
Arizona: Sen. Jeff Flake (R-AZ) retired after only one term because he knew he couldn’t criticize President Trump and win a Republican primary. Overall, polls show that Democrat Kyrsten Sinema is slightly favored to win this seat over Republican Martha McSally.
Mississippi special: Sen. Cindy Hyde-Smith (R-MS) was appointed to replace seven-term incumbent Thad Cochran (R-MS). This seat is mostly vulnerable because far-right Republican state senator Chris McDaniel is likely to not win either of the top two spots for the January runoff. He could then have his stay home and allow Mike Espy (D) to beat Hyde-Smith.
Nevada: Sen. Dean Heller (R-NV) is the only senator up for a second term in a state that Hillary Clinton carried. Polls have been close, but forecasters think he’s somewhat of an underdog against US Rep. Jacky Rosen (D-NV-3) at this point.
Tennessee: Sen. Bob Corker (R-TN)’s retirement after two terms and former Gov. Phil Bredesen (D-TN)’s entry into the race have made this election as competitive as possible. It seemed that US Rep. Marsha Blackburn (R-TN-7) had pulled away, but the race has tightened again in its final weeks.
Texas: Sen. Ted Cruz (R-TX) wants a second term, but US Rep. Beto O’Rourke (D-TX-16) is determined to stop him from getting one. In this perhaps most hyped election of 2018, Cruz’s lead dwindled over the summer before widening again during the fall, but a couple of polls point towards a photo finish. Cruz is still likely to keep his seat, however.
Group IV: Safe Republican-held Seats (4)
Mississippi: Sen. Roger Wicker (R-MS) was first appointed to the Senate to fill Trent Lott (R-MS)’s seat in 2007. He won a special election in 2008 to finish the unexpired term before winning a full term in 2012. He’s running for a second full term. State house minority leader David Baria (D) is dead meat.
Nebraska: Sen. Deb Fischer (R-NE) is running for a second term. Nebraska Democrats’ bench doesn’t exist and hasn’t for awhile, so Lincoln Councilwoman Jane Raybould (D) gets to be the sacrificial lamb.
Utah: Sen. Orrin Hatch (R-UT) is retiring after seven terms, and Mitt Romney (R), the former governor of Massachusetts, would like to fill his seat. So would Jenny Wilson (D), a Salt Lake County Councilwoman. It will be interesting to see if Romney’s victory margin exceeds Wilson’s entire percentage of the vote.
Wyoming: Sen. John Barrasso was first appointed to the Senate fo fill Craig Thomas (R-WY)’s seat in 2007. He won a special election in 2008 to finish the unexpired term before before winning a full term in 2012. He’s running for a second full term. Gary Trauner (D) can look forward to his third loss in a statewide race.
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The bottom line is that although Democrats are highly favored to take the House, Republicans have almost as good odds to hold the Senate. According to FiveThirtyEight’s statistical Senate forecast model, the three most likely outcomes are 51R-49D, then 52R-48D, then 50R-50D. The 80% confidence interval is from 51D-49R to 55R-45D, meaning there’s an 80% chance the outcome falls in that range. Don’t be surprised if little changes in the Senate. Democrats do seem to have the wind at their backs, but no party has ever faced a map with so much unfriendly turf at once.