Both of Georgia’s U.S. senators voted to uphold President Donald Trump’s border emergency on Thursday, standing with the White House even as a dozen of their GOP colleagues bucked the party on constitutional grounds.

Republicans Johnny Isakson and David Perdue voted against Democrats’ resolution of disapproval, which passed the Senate 59 to 41. The president has promised to veto the measure, which is a response to his Feb. 15 move to invoke emergency powers to secure money for a Southwest border wall.

Isaskson did not publicly announce his plans to reject the resolution until an hour before the vote. He had wrestled with the decision for weeks - the fight pitted his party loyalty against his wariness of executive overreach - but Isakson said he ultimately saw it as a question of border security, not the separation of powers.

"The only vote you could take, in my judgment, would be one in favor of security,” he said.

Perdue, a Trump ally who is up for re-election in 2020, declared his intent to vote against the resolution after a trip to the Texas border several weeks ago.

“There is a five-alarm crisis at the southern border. I’ve seen it firsthand,” Perdue said. “This is not just about illegal immigration or building the wall. It’s about the explosion in illegal drug trafficking.”

The White House had dialed up the pressure on Republican senators to stay unified in recent days. Trump tweeted on Thursday morning that "a vote for today's resolution by Republican Senators is a vote for Nancy Pelosi, Crime, and the Open Border Democrats!"

The president even called Isakson on Thursday morning to make his case, but by then the three-term Republican’s mind had been made up.

"Democrats, it was all politics with them," said Isakson, who previously reached across the aisle on immigration legislation but has also voiced support for the wall.

Isakson and Perdue’s pledges to support the president came even without public assurance from the White House that it would rule out siphoning money from Georgia’s military construction projects to pay for the wall.

The law governing emergency powers gives Trump broad authority to divert funding from certain federal programs and projects. One Democratic analysis estimated that $234 million in Georgia military construction funding is eligible to be tapped, including projects at forts Gordon and Benning.

Both Isakson and Perdue have been major boosters of the state's military bases. At the same time, the duo has leaned heavily on the Trump administration as of late to advance two of their top issues: Savannah port funding and a disaster relief bill for Hurricane Michael victims.

The White House previously said it would ask Congress to back-fill funding for military construction projects and insisted nothing would be canceled. Democrats have signaled they’re unlikely to cooperate.

An Isakson spokeswoman said he plans to sign on as a co-sponsor of a bill being offered by GOP colleague Mike Lee that would require congressional approval for future national emergencies.

Trump rejected Lee’s bill on Wednesday - some Republicans had advanced it as a way to tamp down on GOP defections on the border disapproval vote - but suggested he was open to it a day later.

The resolution divided Georgia's 14 lawmakers in the U.S. House along party lines last month.

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