Was the Republican takeover of Congress terrific news for Hillary Clinton, or terrible news for Hillary Clinton? At the moment, our nation’s brave pundit corps is divided on the question.

But one thing is clear: In 2016, the relationship between the president and Congress could have a larger effect on the outcome than in any race since Harry Truman pulled out a surprise victory in 1948 running against a “do-nothing Congress” controlled by Republicans.

For all the talk of Republicans now having an obligation to govern, you’d have to be pretty naïve to think that the next two years are going to feature much besides bitter conflict between President Obama and the opposition. After years of debt ceiling crises, a government shutdown, and general rising contempt on both sides, and likely more of the same for the next two years, the Democratic candidate (and we’ll presume for now it will be Clinton) will have to talk a great deal about how she’ll deal with a Congress likely to be controlled by the other party after 2016.

In recent presidential elections, candidates have gotten away with a good degree of vagueness on this question, arguing simply that they’d reach across the aisle and transcend partisanship, because that’s what the American people want. And it is what a majority of the American people want (at least in the abstract), so the candidates who said that were rewarded: Barack Obama, George W. Bush, and Bill Clinton all promised to be, in Bush’s phrase, uniters and not dividers. All of them would genuinely have liked to be uniters, but it didn’t work out that way.

Now think about the context in which the 2016 race will take place. For much of the last six years, the most aggressive Republican moves, like the dozens of Affordable Care Act vetoes, occurred in the House, and then died in the Senate. President Obama has vetoed only two bills in his entire presidency, fewer than any president since Millard Fillmore. Since Republicans took over in 2010, it’s been a story of simmering resentment punctuated by occasional crises (and one shutdown).

But in the new Congress, bills to directly attack the Obama agenda and legacy won’t founder in the purgatory of the Senate docket. Depending on how aggressively Democrats use the filibuster, they will pass both houses, and end up being vetoed by President Obama — a much more high-profile event. The news out of Washington will be a steady stream of direct, angry, and loud confrontations between the White House and a unified GOP Congress.

Unlike Obama in 2008, Bush in 2000, or Bill Clinton in 1992, Hillary Clinton wouldn’t be running with her own party controlling Capitol Hill. Those candidates could say they’d reach out to the other party, but they and voters knew that if their overtures were rejected, they could still get things accomplished. But faced with the most conservative and obstructionist congressional Republicans in memory, Clinton won’t be able to wish the question away with lofty talk of sitting down to join hands and find common ground.

Clinton may choose to just run against Capitol Hill Republicans: My opponent and the do-nothing Congress are holding the country back, so elect me. But the fact that the conflict between Barack Obama and these Republicans is likely to be even more intense than it has been until now means that the question of how the next president deals with Congress could define the 2016 race.

Clinton can argue that a Republican president and a Republican Congress would be a terrifying combination, and some of us might believe she’s right. But if the only alternative is four more years of bitterness and gridlock, lots of voters could chose to give the GOP the chance to do its worst. If Clinton doesn’t already have a persuasive description of how she will govern if faced with a legislature controlled by Tea Partiers and Republicans afraid of Tea Partiers, who will fight her on every single thing she wants to do, Clinton sure ought to come up with one soon.