The impermeable membrane of partisanship that sheathes American voters’ brains may not be good for the country, but it sure helps forecast congressional races in presidential years.

In five of the six presidential elections this century, the party that won the White House also won or retained a majority in the House of Representatives. Only in 2012, when Republicans were insulated by their 2010 mega-majority—the largest midterm gains by a party out of power since the Great Depression—did voters choose different parties to control the House and the presidency.

With so little split-ticket voting, we have tended to get a lot of sweeps. Voters, especially the substantial chunk of the electorate that turns out only in presidential years, tend to pick one side or the other, not evaluate the merits of the individual candidates for lower offices. That’s particularly true in the House, where many Americans go to vote not sure even of whom their current representative may be.

So what can we figure for the House this year?