If you thought 2016 was a dismal political year, just wait until next year. The polls have tightened since last week, with the news of more e-mail troubles for Hillary Clinton, but the likeliest outcome remains a Clinton victory over Donald Trump, a reduced Republican majority in the House of Representatives, and—the most uncertain element—a narrow Democratic majority in the Senate, perhaps a fifty-fifty split with Tim Kaine, as Vice-President, able to cast tie-breaking votes. And, if the recent statements from Republican senators about blocking any Clinton nominee are borne out, the Supreme Court will remain split, with four liberals and four conservatives, for some time.

In other words, power in Washington will likely be very closely divided, with neither party able to claim true dominance. This could be a recipe for one of the most unproductive two- or four-year periods in political history.

Coöperation between the parties has already nearly evaporated in Washington in recent years. Journalists and scholars cite many factors to explain why this is so: gerrymandered districts, historic levels of ideological polarization, the right-wing media’s influence on Republicans, President Obama’s allegedly poor negotiating skills.

But there is one simple factor that has received much less attention: partisan control of the House and Senate is up for grabs more often than in previous eras. When the party that does not control the White House has a realistic chance of winning a congressional majority in one or both chambers, the incentives for House members and senators to coöperate with the President of the opposing party plummet. When that happens, all of the familiar elements of the permanent campaign—fund-raising, releasing attack ads, using Congress to highlight ideological differences—become more important, while serious efforts at legislating diminish.

Consider how Republican senators will view the political playing field next year if they are narrowly in the minority and Clinton is President. In the 2018 midterm elections, Democrats will be defending twenty-five Senate seats, while Republicans will be defending just eight. The choice between coöperating with Clinton or opposing her on almost every front, as the G.O.P. did with Obama, will be shaped entirely by the fact that Republicans, even if they lose the Senate this year, will have a high chance of winning it back two years from now. In the view of most Republican senators, allowing Clinton to get anything through Congress—or anything done at all—would be the equivalent of handing her victories, strengthening her politically, and reducing their own chances of winning back the Senate.

But what about the embarrassing loss that Republicans might face in 2016? Won’t their lesson be that they need to reach out to Clinton-leaning groups, such as millennials, college-educated voters, and nonwhites? In the short term, the answer may be no.

For one thing, turnout is lower for midterms. The electorate that went to the polls for the 2010 midterms, when Republicans won back the House and expanded their ranks in the Senate, and in 2014, when Republicans took back the Senate and expanded their ranks in the House, looked nothing like the Presidential-year electorates of 2008 and 2012, when Obama won. While congressional Republicans may theoretically be in favor of improving their party’s standing in Presidential-election years, most Republicans, especially in the House, will face a much whiter and older midterm electorate in 2018. For most congressional Republicans, figuring out how the Party can appeal to demographic groups that may help it win back the White House will be somebody else’s job.

But isn’t this sort of hyper-partisan combat the way it has always been? Not really. As Frances Lee, a political scientist at the University of Maryland, points out in a new book, “Insecure Majorities: Congress and the Perpetual Campaign,” when Democrats dominated Congress, from 1933 to 1981—they had an average of sixty per cent of the seats in that period—coöperation from the minority party was high because Republicans had no hope of taking power. But since 1981 the party controlling the Senate has flipped seven times, and the party controlling the House has flipped three times. If Clinton wins, the two parties, assuming she finishes her term, will each have controlled the White House for twenty years.

There are, again, many reasons for why the two parties are more competitive, the most important being the South’s transformation into a Republican stronghold. But Lee argues that the fact that they are so evenly matched is the single biggest explanation driving the kind of partisan conflict that leads to an over-all strategy of non-coöperation and gridlock in Washington.

“It is hard to see how this fall's elections will settle anything in the ongoing power struggle between two evenly matched parties,” Lee told me. “If Clinton wins, congressional Republicans will be looking toward 2018 and a midterm backlash against the President's party that will strengthen their position on Capitol Hill. They will also be looking to do what they can to make Clinton a one-term President. By withholding coöperation, they will be able to forcefully criticize her initiatives and define a set of issues that will help their party make a case for a return to power.” Under these conditions, there are “very few political incentives” for bipartisanship, Lee said. “It is hard to see what reason they'd have to pursue a different course at this juncture.”

How could Clinton, or any President, change this incentive structure? She could find ways to raise the cost for non-coöperation. But Obama found this difficult to do. After all, Republicans still took back the Senate in 2014 after shutting down the government, which is perhaps the most extreme form of non-coöperation available to the out party, and was highly unpopular with the public. As long as the realistic promise of a midterm victory is around the corner, Republicans are unlikely to change course. If Clinton wins, she will have to be far more creative if she wants to change the dysfunction in the capital—and not become a part of it.