When the Senate voted Thursday afternoon to block President Donald Trump's declaration of a national emergency on the southern border, most Republicans stood with the president and opposed the effort.

But none of those "nay" votes seems quite as loud, or discordant, as the one cast by Sen. Ben Sasse (R-Neb.), who is fond of talking about the importance of Congress as a check on runaway executive power but who declined Thursday to play his part in stopping exactly such a power grab. The joint resolution passed easily—59-41, with 12 Republicans supporting it—so Sasse's vote didn't change the outcome, but that really only makes Sasse's opposition more curious.

Even more curious is the statement Sasse provided about the vote.

"We have an obvious crisis at the border," he said, before defending Trump's authority to use the National Emergencies Act of 1976 (NEA) to address it.

"I think that law is overly broad and I want to fix it, but at present Nancy Pelosi doesn't," Sasse said. "As a constitutional conservative, I believe that the NEA currently on the books should be narrowed considerably."

His argument, essentially, is that it's more important to fix the many flaws with the NEA than to block a single instance of executive overreach made possible by the law—a law that he worries will be used by a future Democratic president in more and different ways to trample Congress.

But, c'mon, this isn't a binary choice. Voting to stop Trump's exective flexing doesn't prevent Congress from doing more to limit presidents' authority to use the NEA for politically-motivated national emergencies that really aren't. Sasse could absolutely vote for Thursday's resolution and continue advocating for further congressional action against the NEA—in fact, his position likely would only be bolstered by voting to stop Trump in this instance. That's exactly what a self-identified "constitutional conservative" should do.

Instead, his statement makes it sound like Sasse is in favor of checks and balances for partisan reasons only. That's a shame, because a vote in favor of the resolution would also fit with the concerns Sasse has (repeatedly) expressed about executive overreach and congressional complacency.

Here's Sasse last month in National Review talking about the emergency declaration:

"If we get used to presidents just declaring an emergency any time they can't get what they want from Congress, it will be almost impossible to go back to a Constitutional system of checks and balances. Over the past decades, the legislative branch has given away too much power and the executive branch has taken too much power."

And back in August, Sasse went on a lengthy stem-winder during the confirmation hearing for Supreme Court Justice Brett Kavanaugh, prompting me to praise him for calling out how Congress has abdicated its responsibility to be the nation's law-making authority by handing over power to the executive branch.

"Government is about power. Government is not just another word for things we do together," said Sasse. "Almost all the power right now happens off-stage, and that leaves people wondering 'Who is looking out for me?'"

On Thursday, Sasse had a chance put his vote where his mouth is. He didn't do it. His vote might have been due to fealty to the White House (he had dinner with Trump on Wednesday), or due to concern about future attack ads from a Trump-backed primary challenger (he's up for re-election in 2020), or simply a strategic blunder that was forced upon him by a president from his own party.

Regardless, it will make it more difficult to take him seriously the next time he talks about the dangers of executive power and it should be a blow to Sasse's carefully cultivated image as a thoughtful, independent conservative.