In ways big and small, some congressional Republicans are distancing themselves from President Donald Trump – though at-risk Republicans seem more willing to stick with him as the 2020 elections approach.

Thursday brought a fairly big rebuke: The Republican-run Senate voted 59-41 to nullify Trump's national emergency declaration on border security, with a dozen GOP members voting against their president.

"VETO!" Trump tweeted just moments after the Senate recorded the vote, a day after saying that Republican opposition to the emergency declaration would be "a bad vote."

For the most part, however, Republican senators who face the toughest re-election bids next year stuck with Trump, who continues to enjoy strong support from Republican voters at large.

"It suggests that they see more electoral peril voting against the president than voting with him," said Kyle Kondik, managing editor of Sabato’s Crystal Ball newsletter at the University of Virginia Center for Politics.

Still, the emergency declarations vote magnifies a series of lower-profile disputes between GOP lawmakers and Trump. It signals that the president could meet resistance on policy items ranging from the budget to political appointments to foreign policy initiatives.

Indeed, Trump, who hasn’t vetoed a single bill so far in his presidency, may need the veto pen more frequently in the coming months. If so many Republican were willing to buck Trump on his signature campaign issue – building a border wall – it signals more trouble ahead for him from GOP lawmakers who have until recently been reticent to cross Trump.