The Republican Party that can’t get out of it’s own way is alive and unwell. The party that threw away winnable Senate seats by nominating people such as Todd Akin (Missouri, 2012) and Christine O’Donnell (Delaware, 2010) and couldn’t prevent the nomination of a reality television star for the presidency made a special appearance in the Senate this week. This party is making life difficult for its most vulnerable senators in the 2020 election cycle.

As expected, the Senate voted on Thursday against President Donald Trump’s declaration of a state of emergency over the southern border, with 12 Republicans joining all the Democrats for a 59-41 overall margin. That’s an even larger defeat for Trump than Wednesday’s 54-46 thumping over his Yemen policy. The votes reflected both Majority Leader Mitch McConnell’s inability to hide divisions within the party.

The big surprise, however, is that despite the defections of 12 Republicans on Thursday and seven on Wednesday, three of the most vulnerable Republican Senators in 2020 — Arizona’s Martha McSally, Colorado’s Cory Gardner and North Carolina’s Thom Tillis — stuck with the president on both votes. Of the seven Republican senators running for re-election in 2020 who are not considered “safe” by the Cook Political Report, six were loyal to Trump on both votes. The exception was Susan Collins of Maine.

Given how badly the state of emergency does in public opinion polls, this is highly unusual. Usually it would be the vulnerable politicians who act as moderates, and those with safe seats who are comfortable with ideological extremism. Instead, it seems likely that electoral incentives pushed McSally, Gardner and Tillis away from the center because Republicans politicians are more afraid of primary challenges and threats of withholding party resources for disloyalty than they are afraid of swing voters in their districts.

It’s not clear whether the pressure to vote with the party is mainly coming from Trump or from Tea Party Republicans who have been agitating for radical votes for years, beginning long before Trump. It’s also unclear whether it’s actually true that crossing Trump and Tea Party activists is actually more dangerous for incumbent senators in marginal states. Nevada’s Dean Heller stuck by Trump in 2018, only to be soundly defeated in the general election.

It’shard to imagine that Yemen policy will move many voters. Still, one of the reasons any incumbents win re-election is that they normally work hard to represent their districts. McSally, Gardner and Tillis are choosing a risky path by catering to the conservative side of a very conservative party in states that elect people from both parties.

Bernstein is a Bloomberg News columnist.