Washington (CNN) - President Donald Trump is preparing to issue what is likely to be the first veto of his presidency to protect his national emergency declaration. A critical mass of Republican senators -- 12 in total -- joined Democrats Thursday to pass a resolution rescinding that declaration, despite efforts by both Hill Republicans and the White House to avoid the embarrassment.
What did we learn about Washington in this whole ordeal?
Trump can't be convinced to be helped
Since before the end of the government shutdown, Senate Republicans have been trying to convince Trump that declaring a national emergency to build a border wall was going to be a political problem for the party. It's a poor reflection on both Trump and congressional Republicans that the President seems unable to see what is in his own self interest.
Both publicly and privately, Republican leaders warned Trump he would face resistance from members of his own party. In January, one GOP senator approached the White House Counsel's Office to encourage Trump to embrace the narrowest possible emergency declaration as a buffer against legal challenges and a rebuke from Congress. Trump didn't listen and moved ahead with his national emergency declaration after signing a deal to avoid a shutdown in February.
After House Democrats passed a resolution on Feb. 26 rescinding the declaration, Republicans concerned about the constitutionality of the President's move still thought they had a way out for Trump: support Utah Sen. Mike Lee's bill to end all future emergency declarations after 30 days. If Trump put his weight behind Lee's proposal, enough Republican senators might have been convinced to vote against the House resolution, allowing Trump to save face.
But on Wednesday, Trump called Lee's cell phone during the Senate GOP lunch to inform his fellow Republicans he would not support the bill, according to an aide to the senator. Shortly thereafter, Lee announced he would be voting for the resolution.
Even at the eleventh hour, a trio of Republicans tried to find a way out, traveling to the White House late Wednesday night to find a compromise with the President. Trump wouldn't have it, and was only willing Thursday morning to endorse the idea of reining in national emergency powers after the vote on the resolution.
Pence is not very persuasive
Vice President Mike Pence was dispatched to the Hill to dissuade Republican senators from voting for the resolution. On Feb. 26, Pence and a Department of Justice lawyer spoke at the Senate GOP policy luncheon where they got an earful from senators unmoved by the White House's persuasion.
"I didn't think his argument was very good. 'We've got a crisis, that means the President can do this.' That's essentially the argument," one Republican senator told Politico after the lunch.
Pence's most recent effort was to meet with five wavering senators on Capitol Hill: Sens. Thom Tillis of North Carolina, Pat Toomey of Pennsylvania, Rob Portman of Ohio, Lee, and Lamar Alexander of Tennessee. It didn't work. All but one of them ended up bucking Pence and voting for the resolution.
It wasn't all bad -- after intense lobbying on Thursday, Pence did convince Tillis, who is up for re-election next year, to vote against the resolution. But on balance, Pence was unable to stop a dozen Republican senators from breaking ranks with the White House.
RELATED: These 12 GOP senators voted against Trump's national emergency declaration
That's a bad look for a vice president who serves as the President's chief liaison to Congress. it also comes on the heels of Pence failing to broker a broad immigration deal late last year.
Some Republicans are still willing to stand up to Trump
The President's hold on the GOP only continues to solidify in approval polls and as the 2020 election approaches. But the rebuke from 12 Republican senators suggests there is still a willingness among some to stand up for the constitutionalism that conservatives have espoused for years -- particularly during the Obama administration.
When Barack Obama took executive actions to sidestep Congress and move forward on immigration agenda items, Sens. Rand Paul of Kentucky and Ted Cruz of Texas criticized him for acting like a "monarch" and a "king."
Despite cover from conservative media and talk radio, several Republicans were unwilling to be so blatantly hypocritical. That includes Paul, who voted for the resolution, but not Cruz, who backed the President. Those who didn't cited adherence to the Constitution to justify their votes.
"I support the President on border security," Alexander said. "But his declaration to take an additional $3.6 billion that Congress has appropriated for military hospitals, barracks and schools is inconsistent with the US Constitution that I swore an oath to support and defend."
"This is a vote for the Constitution and for the balance of powers that is at its core," said Sen. Mitt Romney of Utah.
Trump doesn't understand his fellow Republicans
Judging by the President's response, he doesn't seem to buy the constitutionalism defense. He tweeted as much earlier this week.
Trump has also emphasized that voting against the resolution was an endorsement of border security -- and that voting for it was tantamount to voting against border security.
The President isn't wrong about the marker the vote on the resolution represents, but Republicans don't want it framed this way. That's because many of their voters support increased border security, even though Trump's wall has a more broad toxicity among the general public.
Until Thursday, Republicans have avoided taking a vote on the wall, which is how they would have preferred to keep it. Trump's statement of fact -- that voting to keep the emergency declaration is a vote for his wall -- is an inconvenient one for Republican senators, and may put some of them at odds with Trump's base. Shortly after the vote, Trump tweeted a clear message to his supporters about how he intended to respond: "VETO!"