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(CNN) —  

Republicans are on the verge of their second high-stakes votes this week that will test their allegiance to President Donald Trump and force the party to reckon with how far it is willing to let executive power reach.

The votes – first a resolution passed Wednesday that pulls back American aid to Saudi forces in Yemen, followed by a resolution Thursday to block Trump’s emergency declaration on the southern border – have left some in the GOP conflicted about whether they will vote with Trump or protect congressional authority on some of the biggest issues facing the Congress: war and government spending.

The resolutions are both privileged, which means they cannot be stopped by Senate Majority Leader Mitch McConnell, a Republican from Kentucky. And the votes come as the GOP has spent weeks debating how to soften their blow.

Republicans’ hopes all but evaporated Wednesday afternoon after Trump called into the Republican Senate lunch to announce he would not support a proposal from GOP Sens. Mike Lee of Utah and Thom Tillis of North Carolina that would limit the President’s future ability to issue national emergencies. The proposal from had been intended to try to limit the number of Republican defections on the national emergency vote Thursday.

For weeks, Republican senators have been working behind the scenes to try to convince the White House to use other means to build the President’s border wall, including trying to draft a resolution that would have encouraged the White House to find money for the wall through less controversial appropriations transfers rather than the emergency declaration.

But Wednesday, it became clear that the party was out of options and members would be forced to vote to stay with or rebuke Trump on his signature campaign promise.

“It’s over,” one GOP senator told CNN of efforts to find a compromise to give senators concerned about the declaration an off-ramp. “All that’s left to do is to vote.”

Lee announced Wednesday that he will vote for the resolution of disapproval, making him the fifth Republican to say they will join Democrats on Thursday.

Trump confirmed his veto threat for the national emergency resolution in comments from the White House on Wednesday afternoon.

“This is really a vote not on constitutionality, because it’s constitutional,” Trump said about Thursday’s scheduled vote. “It’s not a vote on precedent, because if you take a look at what President Obama did with DACA and so many other things, that was no precedent.”

Later Wednesday afternoon, the Senate voted 54-46 – with seven Republicans joining all Democrats – to pass the resolution curtailing US military support for a Saudi-led war in Yemen. The resolution now goes to the House, which approved a very similar measure earlier this year, to be passed again.

The votes on the Yemen resolution and the emergency declaration represent some of the strongest backlash the President has weathered from his own party yet. They come just months after the midterm elections shattered the President’s reliably Republican-led Congress and ushered in a new Democratic majority in the House dead set on investigating every corner of the Trump administration. Resolutions that once would have languished in a Republican-controlled House are now proposals that sail through the Democratic-controlled body and will finally be delivered to the President’s desk.

“These will be the first two vetoes coming in rapid succession. Maybe Republicans did notice the 2018 election. Maybe they have actually come to the conclusion that blindly following (Trump is) probably not great politics,” said Sen. Chris Murphy, a Democrat from Connecticut who sponsored the Yemen resolution. “I don’t know if they are as afraid of voting against him as they were before 2018. It might not be that they are making a strategic shift but that there is less worry about the consequences.”

The vote on the Yemen resolution was not overwhelmingly Republican, with just seven defections. But aides expected that the vote on the resolution of disapproval on the national emergency declaration could peel off anywhere from 10 to 15 Republicans, a sizable chunk. Lee, Tillis and Republican Sens. Lisa Murkowski of Alaska, Susan Collins of Maine and Rand Paul of Kentucky have all publicly announced their support for the resolution of disapproval, with more Republicans privately wrestling with their votes.

Sen. John Thune, the majority whip from South Dakota, told CNN that there was a bit of “a fatalistic view” that the time had come to vote.

Some Republicans discounted the idea that the party was being torn apart by the back-to-back votes.

“I think that is the legislative process. At the end of the day, the tent is big enough for Republicans to disagree,” said Sen. Tim Scott, a Republican from South Carolina.

“I think these are more issue-driven,” Sen. Jim Risch, an Idaho Republican who’s the chairman of the Senate Foreign Relations Committee, told CNN.

This story has been updated to reflect additional developments Wednesday.

CNN’s Kevin Liptak, Ted Barrett, Clare Foran and Ellie Kaufman contributed to this report.