Ever since Donald Trump won the presidency, 2018’s race for the Senate seemed to pit two powerful, competing forces against one another: the Republicans’ long and enticing list of Democratic targets, several of which are in some of Trump’s best states, versus the longstanding tendency of the president’s party to struggle to make gains in midterm elections.

That second point, on midterm struggles, is not only amplified by the president’s poor approval ratings, but also by some history that is daunting for the president’s party: It’s uncommon for an incumbent in the presidential out party to lose reelection in a midterm.

My Crystal Ball colleague Geoffrey Skelley looked at all of the Senate midterm elections in the popular election era, which dates back a century and includes 26 midterms from 1914 to 2014. He found that Senate incumbents who did not belong to the president’s party have a sterling reelection record: 91% (287 of 314) of non-presidential party incumbents won reelection in midterms.

If anything, out-party incumbents losing in a midterm is becoming less common: In six of the last eight midterms, including the last three (2006, 2010, and 2014), no such incumbent lost reelection.[1] The last three midterms were all conducted under presidents with weak popularity (George W. Bush in 2006, and Barack Obama in 2010 and 2014).

Over the last century, there’s only one midterm where the reelection rate for non-presidential party senators was less than 80%: in 1934, during President Franklin D. Roosevelt’s very successful first midterm, less than half of the GOP incumbents running for reelection (47%) won another term, and that is one of only three midterms since the Civil War where the president’s party also netted seats in the House during a midterm. While we cannot know what the precise circumstances of next year’s election will be, Trump generating a national mandate akin to FDR in the midst of the New Deal seems almost unimaginable, though we must admit our imaginations have been tested in recent years.

As one might expect, the reelection rate of presidential party senators in a midterm year is a still robust but far weaker 75% (291 of 389).

All of the 33 Senate incumbents up for reelection next year are running for another term, at least at the moment. Of those 33, 25 are Democrats (including, for the purposes of this argument, Democratic-caucusing independents Angus King of Maine and Bernie Sanders of Vermont) and eight are Republicans. Applying the historical averages to next year’s Senate elections would result — drumroll please — in a net party change of…zero seats. If 91% of the Democrats/Democratic-caucusing independents are reelected, that would be 23 out of 25, and if 75% of the Republicans are reelected, that would be six of eight, leading to no net change.

Without making any predictions, such a scenario is plausible: Democrats could lose two of the incumbents defending dark red states, in states such as Indiana, Missouri, Montana, North Dakota, and West Virginia, but otherwise hold everything else, while Republicans could lose the only two seemingly vulnerable seats among their much smaller stable of incumbent-held states: Arizona and Nevada.[2]

These historic averages make clear the presidential party midterm penalty, and make it easy to imagine what could’ve happened had the presidential election turned out differently last year. If Hillary Clinton was president, history and the Democratic overextension on the Senate map, not to mention her likely weak approval ratings owing to her negative pre-election favorability, would argue for significant GOP gains. Indeed, just going by the averages, we’d expect the Democrats to lose a half-dozen seats and the GOP to lose one or even zero incumbents. And the net Democratic losses probably would have been even bigger because it’s easy to imagine one or more red state Democrats seeing the writing on the wall and retiring in advance of a tough midterm, giving the Republicans an easy open-seat pickup or two.

Instead, the electoral burden of holding the White House now falls on the Republicans.

The map suggests big Republican gains are possible, but history argues against that possibility. One counterargument to the history is that the country may be more polarized now than in the late 20th century, and therefore Democratic incumbents in deep red states are more vulnerable than they were in previous decades. However, the country was deeply polarized by party in the pre-New Deal era, too, and we saw high midterm reelection rates for non-presidential party senators in that era as well.

Republicans currently hold a 52-48 majority in the Senate, and they would need to gain eight seats to get to the magic 60-seat threshold needed to overcome Democratic filibusters. Such a gain does not seem like a realistic possibility with an unpopular Trump as president, although the map is so attractive that the Republicans easily could start 2019 with more seats than they hold now. A Democratic takeover seems very unlikely given that they have so many seats to defend and only two real targets, Arizona and Nevada. The best possible scenario for Democrats, barring an unexpected vacancy triggering a special election, would seem to be a 50-50 Senate with a Republican vice president breaking ties, and even that seems improbable from the perspective of August 2017.

Regardless, the best bet right now seems to be one in favor of only marginal net change either way in the next Senate.

Map 1 shows our Senate ratings, and Table 1 shows our ratings changes in this update. We are moving two races in favor of the Democrats because of both the overall national political environment and because of the individual circumstances in the respective states. Analysis of all 33 races follows.

Map 1: Crystal Ball Senate ratings

Table 1: Crystal Ball Senate ratings changes

Updates on all the races

For Democrats, there’s no indication that the following incumbents are in any trouble: Sens. Dianne Feinstein (D-CA), Chris Murphy (D-CT), Tom Carper (D-DE), Mazie Hirono (D-HI), Elizabeth Warren (D-MA), Ben Cardin (D-MD), Amy Klobuchar (D-MN), Martin Heinrich (D-NM), Kirsten Gillibrand (D-NY), Sheldon Whitehouse (D-RI), and Maria Cantwell (D-WA). The same goes for Sen. Bernie Sanders (I-VT). Several of these safe senators could be presidential candidates in 2020, and Republicans may have some impetus to try to rough them up in 2018 before the presidential derby gets underway in earnest. As of now, Warren seems the likeliest to have a credible challenger.

The other independent, Sen. Angus King of Maine, also seems to be in decent shape, but his race could become harder if term-limited outgoing Gov. Paul LePage (R-ME) follows through on his occasional threats to challenge the first-term incumbent. King probably would be favored in any event, but a LePage entry could force national Democrats to spend on the independent senator, dollars that they surely could use elsewhere. Sen. Tim Kaine (D-VA), Clinton’s 2016 running mate, is in a similar situation, and he too could face a loud, controversial opponent: Prince William County Board of Supervisors Chairman Corey Stewart (R), who parlayed his defense of Confederate monuments in the commonwealth into a surprisingly close loss against former Republican National Committee Chairman Ed Gillespie (R) in the GOP gubernatorial primary earlier this year. Assuming Stewart’s the nominee — it’s unclear whether any other notable Republicans will run — he will get a lot of attention but would be a major underdog against Kaine, who is well-regarded in a state that is trending Democratic.

Republicans shouldn’t have any business competing for New Jersey, but it’s not out of the question that they could hold the seat for a period of time between now and November 2018. That’s because Sen. Robert Menendez’s (D-NJ) federal corruption case is due to begin soon. The New York Times’ Shane Goldmacher recently examined the various possibilities, and if Menendez were to be convicted and then expelled from the Senate prior to early January, outgoing Gov. Chris Christie (R-NJ) could appoint a Republican to finish out his term. That could have wide-ranging consequences, including providing the GOP with an extra vote to force through its stalled revision of the Affordable Care Act. However, two-thirds of the Senate is required to expel a senator, so even if Menendez is convicted, Democrats could potentially slow-play his expulsion until Phil Murphy (D), a big favorite to win the Garden State’s governorship this November, hypothetically takes office in January and could appoint a Democratic replacement. Anyway, New Jersey seems very likely to elect a Democratic senator next year, be it Menendez or someone else, but the road to that election is rockier than it otherwise should be for Democrats.

On the Republican side, incumbent Sens. Roger Wicker (R-MS), Deb Fischer (R-NE), Bob Corker (R-TN), Orrin Hatch (R-UT), and John Barrasso (R-WY) are highly unlikely to draw credible opposition from Democrats: If any of these races become interesting in a general election, we will know that the Republicans are heading for a really bad year. Hatch, who promised in 2012 not to run for another term, seems intent on running again anyway, and he could potentially face a primary. Corker’s first election in 2006, during the Democrats’ last good midterm, was close and competitive, but Tennessee has become so Republican that it’s hard to imagine the two-term incumbent really having a race.

Texas, where Sen. Ted Cruz (R) is seeking a second term, is close-to but not-quite safe. While the state did shift toward the Democrats in 2016, Trump still won it by nine points, and Democrats haven’t competed statewide in almost a generation: In the nine regular Senate elections since Democrats last won a Senate race in Texas (1988, when Lloyd Bentsen was reelected while concurrently serving as losing Democratic presidential nominee Michael Dukakis’ running mate), Democrats have only averaged 39% of the vote. In Rep. Beto O’Rourke (D, TX-16), Democrats do have a real candidate, and he raised a non-insignificant sum of money ($2.1 million) in the second quarter. However, let’s remember that Texas is a giant, heavily populated state with several big, expensive media markets, so that sum of money wouldn’t go nearly as far there as it would in almost any other state. If O’Rourke is going to make this a race, he’s going to have to do so without much national Democratic help, because groups like the Democratic Senatorial Campaign Committee likely just won’t have the money to chase waterfalls in Texas, which behind California is the nation’s second-most populous state.

Let’s now focus on the dozen races that seem more competitive than the ones already mentioned. Of these, 10 are held by Democrats, and Trump won all 10 of these states in last year’s presidential election. The other two are held by Republicans. Let’s look at those states first.

Sen. Dean Heller (R-NV) is running for a second term, and we recently moved that race from Leans Republican to Toss-up. We do not have much to add, although since that report Heller has received a credible primary challenger, perennial candidate Danny Tarkanian (R), who has tried but failed (sometimes narrowly) to win several races over the last decade and a half. An incumbent senator is usually a heavy favorite in a primary, but Tarkanian’s run just adds to Heller’s difficulties in a Clinton-won swing state.

Joining Heller in the Toss-up category is Sen. Jeff Flake (R-AZ), who we are downgrading this week from Leans Republican. Flake may be something of a man without a party. He is a stalwart conservative on most issues, but he also has been highly critical of President Trump. Because of his conservatism, Flake lacks the general election crossover appeal of his fellow senator, the long-tenured John McCain (R-AZ), and because of his criticism of Trump, he may have trouble in a primary. Trump has criticized Flake, including during a Tuesday night rally in Phoenix, and seemed to recently endorse his primary challenger, former state Sen. Kelli Ward (R), a fringe candidate who nonetheless held McCain to just an 11-point victory in last year’s Republican Senate primary. While she is not yet an announced candidate, Rep. Kyrsten Sinema (D, AZ-9), a proven fundraiser and electoral performer in a Democratic-leaning swing district with a centrist voting record, seems very likely to run. Given Flake’s challenges, the national environment, and Sinema’s potential as a challenger, this race increasingly looks like a coin flip.

So the good news for Democrats is that they appear well on their way to running formidable challenges to the two most vulnerable GOP Senate incumbents. The bad news for them is that, among the most clearly competitive seats, they are playing defense everywhere else.

Let’s start in the two states that hypothetically should be the easiest for them to hold, Michigan and Pennsylvania. They, like New Jersey and Virginia, are rated as Likely Democratic, but we include them here as potentially more fruitful GOP targets, both because of the states’ 2016 turn toward Trump and also because of the potential for intriguing Republican nominees against Sens. Debbie Stabenow (D-MI) and Bob Casey (D-PA).

In the Keystone State, it appears as though Trump ally Rep. Lou Barletta (R, PA-11) is going to run. While there are other candidates running, Barletta would have the biggest profile, although Casey’s two victories both have been fairly comfortable. In the Wolverine State, one cannot ignore the possibility that Robert Ritchie (R), the musician otherwise known as Kid Rock, could run, although our sources don’t seem to think he’ll follow through with his rumored campaign (he has been relatively quiet since making noise about running in July). Some Republicans would welcome his campaign, though: The president of Senate Leadership Fund, a well-funded shadow National Republican Senatorial Committee that is close to Senate Majority Leader Mitch McConnell (R-KY), has said he hopes Kid Rock does run. It’s not hard to see Kid Rock outrunning usual GOP Senate performance in Michigan: Since 2000, when Stabenow beat incumbent Sen. Spencer Abraham (R-MI) in a very close race, there have been five Senate elections in Michigan, and the average Democratic margin of victory has been 20 points. It may be that Michigan and Pennsylvania should be judged not by whether Stabenow and Casey win, but rather by what kind of investment Democrats have to make in order to carry them to victory. Dollars that could be spent in these two states may end up being needed in other places. If either Stabenow or Casey lose, the Democrats likely will have had a disastrously bad midterm.

A potentially better Republican target is Wisconsin, given that Sen. Tammy Baldwin (D) is only running for her second term and the GOP state organization there is quite strong. The candidate field is not that clear, though, and there could be a bitter primary among state Sen. Leah Vukmir, Marine veteran Kevin Nicholson (an ex-Democrat backed by the economically conservative Club for Growth), and others. Baldwin benefited from a tough, late GOP primary in 2012, and the 2018 primary will also be in August.

The Badger State, along with Michigan and Pennsylvania, were the difference in last year’s presidential election: had Clinton won all three states, which were decided by a combined 77,744 votes, she would have been president. Trump’s approval ratings in all three states are in the low 40s or worse, so he could be a drag there, just like Barack Obama was in 2010 when, just two years after all three states gave him comfortable victories, they swung heavily to the Republicans at the gubernatorial and federal levels (and then again voted for Obama in 2012). In politics, things can change in a hurry.

In Ohio, a rematch between Sen. Sherrod Brown (D) and term-limited state Treasurer Josh Mandel (R) seems likely, and Brown is endangered by the state’s strong swing to Trump last year — indeed, Mandel’s hopes rest on the possibility that Ohio is now functionally a clear Republican state at the federal level, as opposed to a swing state with a small GOP lean, as it had been prior to 2016. However, the populist Brown is definitely a better fit for the Buckeye State than Clinton was, and he outperformed Obama’s margin when he defeated Mandel in 2012. Some Republicans are cool on Mandel’s candidacy and believe he is a rather shameless publicity-seeker who never stopped running for Senate after his 2012 loss. Mandel has emulated Trump in several ways, and he outraged many recently by taking the side of pro-Trump Twitter trolls against the Anti-Defamation League (Mandel is Jewish himself). Despite it all, Mandel should be well-funded and he poses a real threat to Brown. There is another notable GOP candidate, Cleveland-area businessman Mike Gibbons. He has no statewide name ID but he has hired credible staffers, some of whom are close to term-limited Gov. John Kasich (R-OH), who has a bad relationship with Mandel. But it’s hard to see Gibbons giving Mandel a real run in a Republican primary.

Even though Sen. Bill Nelson (D-FL) is a proven vote-getter, Democrats are deeply worried about the likely candidacy of outgoing Gov. Rick Scott (R). There are two ways of looking at the potential Nelson-Scott matchup. The first is that while Nelson has won his last two races by convincing margins, Scott barely squeaked by in his two victories in 2010 and 2014, failing to win a majority of the vote either time in what were optimal Republican years and despite dramatically outspending his rivals thanks to his immense personal wealth. That’s the pro-Nelson view. The pro-Scott view is that his personal largesse, combined with that of pro-Republican outside groups, could overwhelm the combined Democratic effort, and that Scott is arguably more appealing now than he was in 2010 and 2014 (Morning Consult pegged his approval recently at a decent 52%) and a more formidable Nelson opponent than the incumbent’s weaker challengers in 2006 and 2012. Nelson is favored for now but this could be a Toss-up in the future. One danger for Republicans is that if Scott decides to not get in, they may be without a backup plan, although the GOP bench in the state is strong. And it seems like the main question for Scott is not if he runs, but when he announces.

The remaining five Senate races all feature Democratic incumbents running in states where Trump ran at least 20 points or more ahead of his national margin. These are hypothetically the best GOP targets, although it may be that by the time next fall rolls around, Republican odds may be better in states like Florida or Wisconsin than in one or more of these states. Still, these are all viable targets, though we see subtle differences among them.

Ask any Senate observer or campaign participant which Democratic senator is most vulnerable and you’re likely to get one of two responses: either Sens. Joe Donnelly (D-IN) or Claire McCaskill (D-MO). The reason these two stand out is that arguably both should have lost in 2012, but they benefited from weak, gaffe-prone opponents. Republicans feel confident they will have better challengers this time: state Attorney General Josh Hawley (R) seems likely to enter in Missouri and will be the primary favorite, and either Reps. Luke Messer (R, IN-6) or Todd Rokita (R, IN-4) should advance to challenge Donnelly in Indiana. No one will outwork Donnelly and McCaskill, but there may be a lowering ceiling on potential support for Democrats in both of these states: Democrats fielded strong Senate and gubernatorial candidates in each state last year, and the highest percentage any of them got was former Missouri Secretary of State Jason Kander (D), who won 46%, losing by less than three points to Sen. Roy Blunt (R-MO). Then again, that was with Obama in the White House, and Trump being president helps Democrats all across the country, even in states that strongly backed him, just because of the usual out-party advantage in midterms. One potential new vulnerability for Donnelly is a recent Associated Press report that his family’s company benefited from low-cost Mexican labor even as Donnelly has argued against outsourcing. Republicans have started calling Donnelly “Mexico Joe,” and we can imagine the attack resonating.

Prior to this update, we included a third Democratic senator from a strong Trump state, Sen. Heidi Heitkamp of North Dakota, in the Toss-up category along with McCaskill and Donnelly, but we’re giving her a boost to Leans Democratic. Heitkamp has a strong personal brand and Republicans do not yet have a clear challenger. She finally got an opponent, wealthy state Sen. Tom Campbell (R), and some Republicans prefer him to Rep. Kevin Cramer (R, ND-AL), who remains undecided on a campaign. Despite North Dakota’s strong GOP lean, Democrats have actually won 11 of the state’s last 13 Senate contests, and we think Heitkamp deserves the benefit of the doubt. Her position is similar to that of Sens. Joe Manchin (D-WV) and Jon Tester (D-MT) — she can generate split-tickets in a very tough state. Heitkamp has not officially announced a reelection bid but is widely expected to do so, and she has been raising money like she is seeking another term.

Manchin, increasingly isolated as West Virginia’s once-mighty Democratic Party withers (newly-elected Gov. Jim Justice recently switched parties and became a Republican), is going to have a strong opponent: Rep. Evan Jenkins (R, WV-3) or state Attorney General Patrick Morrisey (R), although those two are engaged in a very bitter primary. Tester dodged two potentially strong opponents when former Rep. Ryan Zinke (R, MT-AL) became U.S. interior secretary and state Attorney General Tim Fox (R) decided not to run. State Auditor Matt Rosendale (R) and others are competing for the nomination.

Conclusion: Will a senator retire?

Right now we have four Toss-ups: two held by Republicans, and two held by Democrats. If one assumes a 50-50 split on the Toss-ups, and every other seat goes the way we currently rate it, there would be no net change in the Senate. Given the map, that would be a substantial Democratic accomplishment and a missed opportunity for Republicans. But the election’s a long way off and the potential exists for Republicans to make gains next year, too, even if the president’s approval rating doesn’t improve. That would be an unusual result historically, but history is merely a guide. It guarantees nothing, particularly on a Senate map where Democrats are stretched historically thin.

One final point: It is highly unusual that there have not been any retirements so far. Usually there are at least a couple of open seats, and typically more than that, according to the University of Minnesota Humphrey School of Public Affairs’ Smart Politics blog. This is just a guess, but there probably will be at least an open seat or two by the time we get to next fall. Maybe one of the long-rumored retirees, like Feinstein in California or Hatch in Utah, ultimately opts to retire after making moves in recent months to run again. Such a retirement would do little to the Senate bottom line because both of those states lean so heavily to one party. More impactful would be a shocker that truly changes the calculus in one of these states — like one of the Toss-up senators making the calculation later this cycle that they don’t have a path to another term, or that they don’t want another term.

We have no inside information indicating a shock retirement is coming or is even likely. After all, if we knew about it advance, it wouldn’t be a shock. But just because there hasn’t been a retirement yet doesn’t mean there won’t be one, or more, later.

Footnotes

[1.] One has to go back to 2002 to find the last two instances of a non-presidential party incumbent losing in a midterm: Sen. Max Cleland (D-GA) lost to Saxby Chambliss (R) in a bitter race, and Sen. Jean Carnahan (D-MO) lost a very close contest to Jim Talent (R). And 2002 may not be all that comparable to 2018: roughly two-thirds of the nation approved of President George W. Bush going into that election, a far cry from where Trump is, at least at the moment (under 40% approval in averages).

[2.] Alabama, which is holding a special election later this year for the remainder of now-Attorney General Jeff Sessions’ (R) term, is not counted here. We’re only counting the 33 Senate seats with regularly-scheduled elections in November 2018.