It seems like Pennsylvania didn’t get the memo on “The Resistance”—Senator Bob Casey, a Democrat who faces voters in 2018, is dropping in the polls and is now considered vulnerable for re-election.

Just 28 percent believe Casey is doing a “good” job as Senator, while 45 percent feel he’s doing a “fair” or “poor” job. Worse for Casey, his “poor” rating has climbed three points since February—suggesting that voters’ opinions of him are worsening.

Casey was last elected in 2012, when he faced a far more favorable environment with Barack Obama at the top of the ticket. In 2018, he finds himself in a newly-red state: Pennsylvania hadn’t voted for a Republican since Ronald Reagan’s 49-state sweep in 1984—but they came out in full force for Donald Trump.

But despite the fact that Trump won 48 percent of Pennsylvania voters in 2016, Casey has refused to play nice.

While most swing state Democrats have been lying low, fearful of alienating the constituents who just seven months ago voted for Trump, Casey has declared himself part of the “Resistance.” Casey refused to even consider voting on the Republican’s healthcare bill, and just last week, he referred to Trump’s firing of FBI Director James Comey as “Nixonian.”

The fact that Casey, a two-term Senator who won nearly 54% of the vote in 2012, is vulnerable suggests that the Republican wave once-solid blue states in the Midwest, like Michigan, Pennsylvania, and Wisconsin might not be a fluke—and they could continue to vote red even without Trump on the ballot.