How much does a Donald Trump nomination endanger the GOP Senate majority?

Maybe not that much at all. A series of polls in the past week point to a much closer presidential race than preceding surveys: Reuters puts Hillary Clinton up by just one point nationally; Public Policy Polling puts her up by only four points; and Quinnipiac found Trump and Clinton within the margin of error in three swing states that feature key Senate races (Ohio, Pennsylvania, and Florida).

Or maybe all of that is whistling past the graveyard, a brief polling bump reflecting Trump’s victorious status and Clinton’s still losing primaries to Bernie Sanders.

To win back the Senate, Democrats need to pick up either four seats and the presidency or five seats without the presidency. Republicans are trying to hold on to 24 seats, and a slew of them in states that trend blue in presidential years. Besides the big three swing states mentioned above, they’re trying to reelect GOP incumbents in Illinois, Wisconsin, and New Hampshire. Voter turnout in presidential years is usually higher and more diverse than in midterm years, and the likely GOP nominee, Trump, has awful approval numbers among women, Latinos, African Americans, and young voters. The ingredients are there for a wipeout, and after 2006, 2008, and 2012, Republicans know that when it can rain, it can pour.