Exit polls now track a powerful connection between attitudes toward the president and votes in both House and Senate elections. In the past three mid-term elections—2006, 2010 and 2014—exit polls found that between 84 and 87 percent of voters who approved of the president’s performance voted for his party’s candidates in House elections. Simultaneously, 82 to 84 percent of those who disapproved of the president’s performance voted against his party’s House candidates. Since most voters in each election disapproved of the president’s performance, his party suffered substantial House losses each time.

The general assumption among political operatives is that because Senators are better known and raise more money to create an independent identity through television advertising, it’s easier for them than House members to resist this trend. And in almost every election cycle there are Senators who conspicuously notch victories in states that lean the other way in their presidential preference. For instance, two of the most threatened Democratic Senators in this election—Claire McCaskill in Missouri and Joe Donnelly in Indiana—won in 2012 while their states were voting for Mitt Romney over Barack Obama, largely because each benefited from a deeply flawed opponent.

The general trend, though, is for Senate races also to increasingly align with attitudes toward the president.