On November 6th (and for several weeks before, in the many states that permit early voting), Americans will go to the polls to choose all 435 members of the House of Representatives, 35 of the 100 Senators, and a variety of state and local officials. Currently, Republicans hold a dominant position in U.S. politics, controlling the presidency, both houses of Congress, and a strong majority of governorships and state legislative chambers. Democrats are almost certain to make gains—having been reduced to their weakest overall position since the 1920s, they have vastly more pickup opportunities than do Republicans should the pendulum swing back even a bit in their direction. The magnitude of those gains, however, remains very much an open question. Will we see only modest shifts that leave the fundamental partisan dynamics more or less intact, or will we witness a “Blue Wave” that will deliver Democrats control of both houses of Congress and massive gains at the state level? The answer will have important implications for the remaining two years of Donald Trump’s (first?) presidential term.
There are significant reasons for Democratic optimism. Their candidates have performed very well in a series of special elections in 2017 and 2018, typically exceeding the “normal” Democratic vote share in the relevant jurisdiction by a significant margin. They have had great success with both candidate recruitment and fundraising, and are thus poised to be competitive in a range of Republican-leaning areas. The “generic ballot” question, in which pollsters ask whether respondents would be inclined to support an unnamed Republican or Democratic candidate for Congress in their district, is currently showing about an 8-point advantage for Democrats. Finally, history is clearly on their side; the president’s party has lost House seats in 18 of the last 20 mid-term elections, generally (though less consistently) accompanied by Senate and gubernatorial losses as well. Mobilization is typically easier for the party out of power, as their supporters are galvanized by opposition to the president while his own supporters can become complacent. This is especially true when the president is unpopular, and Trump’s abrasive style, chaotic administration, and running war with the media have served to mire his approval ratings in the low- to mid-40s—not abysmal, but also not encouraging to Republicans trying to resist the tides of midterm electoral history.
On the other hand, Republicans do have some reasons to hope that they can blunt Democratic gains. Most importantly, objective conditions in the country are quite good. U.S. economic growth is strong, unemployment is very low, illegal immigrant flows have declined considerably, and ISIS has essentially been defeated. People can argue about how much any of these outcomes is attributable to President Trump, but when conditions are good, the president’s party tends to get some measure of credit. In addition, the electoral map favors the Republicans. In the Senate, 26 of the 35 seats being contested this cycle are currently held by Democrats, including 10 in states that Trump carried in 2016. By contrast, only 4 Republican seats are thought to be plausibly vulnerable. On the House side, Democrats’ tendency to cluster in large cities, combined with Republican-friendly district boundaries in many states, renders Democratic votes less efficiently distributed for purposes of winning a congressional majority. Experts typically estimate that Democrats would need to win the national congressional vote by about 6% in order to capture a House majority. Finally, the Republicans’ traditional core supporters—older, whiter, more affluent voters—are the ones most likely to vote in midterms, where turnout is lower than in presidential election years.
Given this set of conflicting considerations, a range of outcomes is possible. It is likely that Democrats will capture the House (which would require a net pickup of 23 seats), probably by a fairly narrow margin. Conversely, it is likely that Republicans will retain their majority in the Senate; they could lose 1 net seat and retain control, because the tie-breaking vote in a 50-50 Senate would be cast by Vice President Pence. It is important to keep in mind, however, that results of individual races in a congressional midterm tend to be correlated; more often than not, a clear majority of the contests deemed to be “tossups” fall in the same direction. Thus, scenarios in which Democrats decisively capture both chambers and in which Republicans maintain control of both are very plausible.
So what are the implications for President Trump, and for American policy, under various potential outcomes? If Democrats capture the House, but not the Senate (the most probable scenario according to polls, models, and betting lines), the impact is likely to be relatively modest. President Trump’s signature tax cut has already been passed and signed into law, and he really hasn’t announced any other major legislative initiatives since his attempt to repeal “Obamacare” was defeated. Most of his initiatives at this point seem to be taking the form of executive orders, judicial appointments, and international negotiations, none of which the House has much ability to influence. Given the aforementioned history, minor to moderate House seat losses in a midterm are widely expected, so the political fallout to Trump from such an outcome is likely containable. Moreover, as he will no doubt remind people, Presidents Reagan, Clinton, and Obama all won re-election after their parties suffered significant defeats in their first midterms. The only real risk to Trump from a Democratic House would be the investigative power; there would be tremendous pressure from the Democratic base to launch all sorts of inquiries into Trump’s business dealings, his relations with Russia, his personal conduct, etc. Americans have shown in the past, however, that their patience for such inquiries is limited; barring unambiguous evidence of serious wrong-doing by the president himself, such investigations are likely to involve much sound and fury, signifying nothing.
The real danger to President Trump’s agenda and political position would be a Democratic takeover of the Senate. Given how favorable the Senate terrain is to Republicans this electoral cycle, such an outcome would be seen as a real political debacle, and would invite recriminations from within the party. It would likely signal a broader wipeout for Republicans up and down the ballot, and would thus increase the credibility and profile of the anti-Trump faction within the party and make a serious primary challenge to Trump in 2020 more likely. In the short term, a Democratic Senate would make Trump’s quest to transform the federal judiciary much more difficult. Democrats would likely simply refuse to confirm solidly conservative nominees to the courts, forcing Trump to appoint people with moderate or ambiguous records to the bench. This would blunt what many in Trump’s base see as one of the greatest advantages of his presidency. In addition, if Democrats control both houses of Congress, they can advance popular liberal proposals in areas like immigration, healthcare, education, and marijuana legalization to President Trump’s desk. Even if he vetoes them, they will have forced him to take unpopular stances in advance of the 2020 elections. So for those watching on election night, the place to focus is on the competitive Senate races; they will tell the tale of whether the Democratic tide in 2018 is a wave or a ripple.