Republicans in the House largely fell in line behind Trump, under immense pressure from GOP leaders, White House aides and the president himself.

Still, Democratic leaders made a last-ditch attempt to shore up GOP support on Tuesday, with dramatic floor speeches that referenced the Founding Fathers and Martin Luther King Jr., to argue against what they called Trump’s unconstitutional power grab.

“That’s how despots take power,” House Majority Leader Steny Hoyer (D-Md.) said on the floor before the vote.

“Fidelity to the president, or fidelity to the Constitution. That is the choice we make today. That is why this is a pivotal moment,” Hoyer declared.

“We have a constitutional mission and a mandate to preserve the balance of power and to oppose this monument of hate,” Rep. John Lewis (D-Ga.), a civil rights icon, said in another fiery floor speech ahead of the vote.

Some Republicans have echoed similar constitutional concerns. The small House Liberty Caucus — led by libertarian Rep. Justin Amash (R-Mich.) — urged support for the measure.

“This national emergency declaration does not conform to our constitution,” the group, which has eight members, wrote in a statement.

In the Senate, Democrats are inching toward a victory. Just one more GOP supporter is needed to send the measure to Trump’s desk. Congress has never previously voted to overturn a president’s national emergency declaration.

So far, three Republican senators —. Susan Collins of Maine, Lisa Murkowski of Alaska and Thom Tillis of North Carolina — have signaled they would support the measure to overturn Trump’s national emergency declaration over border security. Several other Republicans have declined to disclose their plans but have voiced concerns for weeks, putting Trump on the verge of an embarrassing repudiation, even if he can veto the legislation.

House Speaker Nancy Pelosi (D-Calif.) and her deputies have spent weeks pitching the measure as a constitutional duty, rather than as a partisan ploy by newly emboldened Democrats who seem eager to humiliate Trump.

“This is the most significant vote that this Congress has taken, probably in a generation, on the balances of powers between the president and Congress,” Rep. Joaquin Castro (D-Texas), who drafted the resolution, told reporters Tuesday before the vote.

Democrats are likely to take on the president through the courts; 16 states have launched a legal challenge to block Trump’s national emergency declaration.

Castro and Democratic leaders have targeted their outreach to Republican lawmakers who have been skeptical of the legality of the president’s action.

“I think it’s tough for them because many do respect the Constitution, and at the same time, they’re afraid of being out of favor with Donald Trump and getting a primary opponent,” Castro said.

Democrats had hoped to win over support from GOP defense hawks, many of whom have privately lashed out at the White House’s plan to raid the Pentagon’s construction budget to fund a border wall. The House’s spending panel had been circulating a list of hundreds of projects from Kentucky to Alaska that could be affected by Trump’s tactics.

But most Republicans were unwilling to take a public stand against Trump over legislation that he has said he would “100 percent” veto — which would be the first of his presidency.

The White House threatened the veto on Tuesday afternoon, while offering a preview of its own legal defense. Administration officials argued that the situation on the border is an emergency, citing “sharp increases” in the number of families and unaccompanied minors crossing the border in recent years.

The number of people apprehended at the southern border rose about 30 percent from 2017 to 2018, including a 40 percent increase in families, according to U.S. customs officials. Both figures are down from 2016 numbers, however.

White House officials also argued that former Presidents George W. Bush and Barack Obama used the same authority for “more than 18 different military construction projects between 2001 and 2013.”

Castro acknowledged Tuesday that House Democrats would face an “uphill battle” in overriding Trump’s veto, which would require more than 50 Republicans in the House. “But we’re going to keep working at it,” Castro said.

Republicans, including senior members of the party’s leadership, had been skittish about the White House circumventing Congress to build a border wall even before Trump made the declaration. Many lawmakers said they had hoped he wouldn’t take such a drastic step.

Several acknowledged that backing Trump on the emergency order would amount to hypocrisy after Republicans railed against Obama for his own unilateral actions on immigration as president.

Even this week, Republicans like Rep. Tom Cole of Oklahomacalled the White House’s move an “unwelcome precedent,” while nonetheless vowing to vote against Democrats on the floor.

White House officials, along with the Department of Defense, have mounted a behind-the-scenes lobbying campaign to ease some GOP lawmakers’ anxiety about the president’s move.

Rep. Roger Williams (R-Texas), for example, said he was reassured last week that Pentagon funding would continue to flow to Fort Hood — one of the military’s largest outposts in the U.S. — which lies in his district.

“I’ve been told now by the powers that be that existing construction won’t be affected,” Williams said Monday night, adding that he plans to vote against the Democratic measure.

Melanie Zanona contributed to this report.