WASHINGTON — Senator Rand Paul, Republican of Kentucky, said on Sunday that he would support a resolution that would overturn President Trump’s declaration of a national emergency at the southern border, appearing to provide the crucial vote needed for the Senate to pass the measure.
“I stand with the president often, and I do so with a loud voice,” Mr. Paul wrote in an opinion piece published late Sunday on Fox News’s website. “Today, I think he’s wrong, not on policy, but in seeking to expand the powers of the presidency beyond their constitutional limits.”
“I cannot support the use of emergency powers to get more funding” for a wall along the border with Mexico, he wrote, “so I will be voting to disapprove of his declaration when it comes before the Senate.”
Mr. Paul joins three other Republican senators — Susan Collins of Maine, Thom Tillis of North Carolina and Lisa Murkowski of Alaska — in backing the resolution. His support appears to provide the slim majority Democrats need to send the measure to the president’s desk, offering a stinging repudiation of the declaration.
The House, largely on party lines, passed the resolution on Tuesday, and under the National Emergencies Act of 1976, the Senate is required to vote on the resolution in the coming weeks. Mr. Trump has said he would veto the measure, and it is unlikely that either chamber could muster the two-thirds majority needed to override a veto.
But with several lawsuits already filed in court, a resolution of disapproval from Congress — the simplest mechanism for lawmakers to challenge a declaration — could help opponents of the declaration.
Mr. Paul, a Kentucky libertarian who frequently rails against government spending and often has no qualms about bucking his party, urged his Republican colleagues to recall their frustration with President Barack Obama’s use of executive power. He warned about the legal merits of the order, writing that “I think the president’s own picks to the Supreme Court may rebuke him on this.”
He had signaled in remarks on Saturday at the Southern Kentucky Lincoln Day Dinner that he would vote for the resolution, saying he was opposed to giving “extra-constitutional powers to the president,” according to The Bowling Green Daily News.
But with time before the Senate has to vote, Mr. Trump and his allies have an opportunity to lobby Mr. Paul. Such tactics have been successful before: The Senate Foreign Relations Committee was poised to give Mike Pompeo’s nomination as secretary of state an unfavorable recommendation until Mr. Paul bowed to pressure and gave his approval.
Mr. Trump, who was repeatedly denied wall funding by lawmakers, hopes to use $3.6 billion from military construction projects to fulfill his campaign promise to build a wall along the southern border. He has dismissed concerns about the precedent, saying in a speech on Saturday that “they’re going to do that anyway, folks.”
Some Republican senators — including Senator James M. Inhofe of Oklahoma, the chairman of the Senate Armed Services Committee — have voiced concerns about the effect on military readiness, seeking assurances that projects in their states will not be affected. The Defense Department has yet to release a list of projects affected.
Others, including Mr. Paul, have objected to a possible overreach of executive power that future presidents could take advantage of. But few have been willing to publicly say how they will vote on the resolution.
Senator Lamar Alexander, Republican of Tennessee, said it was “unnecessary and unwise to turn a border crisis into a constitutional crisis about the separation of powers” in a floor speech on Thursday, where he outlined other means for obtaining funds.
“There is no limit to the imagination of what the next left-wing president could do to harm our country with this precedent,” he added. But pressed by reporters, he declined to reveal his planned vote.
“I learned a long time ago in the United States Senate, it’s not wise to announce how you will vote on a vote you may never have to take,” he said.
Conversely, Ms. Collins joined Senator Tom Udall, Democrat of New Mexico, in introducing a resolution of disapproval on Thursday. Ms. Murkowski joined the pair in co-sponsoring the resolution.