Gov. Robert Bentley of Alabama has learned that even your political base is willing to put up with only so much. Bentley, facing impeachment for allegedly using his office to start and cover up an an extramarital affair, reportedly agreed to resign on Monday. What’s so amazing about Bentley’s downfall is that it happened in a one-party setting: Bentley is a Republican, and Alabama’s state legislature and electorate are both overwhelmingly Republican. In these uber-partisan times, it can seem like Democrats always back Democrats and Republicans always back Republicans. That didn’t happen in Alabama.

Indeed, Bentley was, as of last fall, the most disliked governor in the nation among his own party’s voters. Last October and November, the Cooperative Congressional Election Study asked respondents in 50 states whether they approved or disapproved of the job their governor was doing. Just 42 percent of Alabama Republicans said they approved of the job Bentley was doing; 54 percent said they disapproved. No other current governor registered greater than 50 percent disapproval among his or her own party’s voters. In fact, no other governor had a net negative job approval rating with their own party. That includes the historically unpopular Chris Christie in New Jersey.

Partisanship goes a long ways these days. But there are limits.