The border wall promise then-candidate Donald Trump made during his 2016 presidential run was one of the things that got him elected, and now that he’s fighting tooth and nail for it, any backing away from it would be the arrow to his heel that brings him down.

At least that’s why Sen. Lindsey Graham (R-S.C.) says.

According to The Hill, Graham believes that Trump backing down on border security now would likely be “the end of his presidency”:

“He’s not going to sign a bill that doesn’t have money for the wall. I can tell you exactly how this is going to end. The president is going to challenge Democrats to compromise and if they continue to say no, they’re going to pay the price with the American people,” Graham said during an appearance on Fox News’s “Hannity.”

“If he gives in now, that’s the end of 2019 in terms of him being an effective president,” he continued. “That’s the probably the end of his presidency. Donald Trump has made a promise to the American people. He’s going to secure our border.”

Graham doesn’t just believe it would have a negative effect on Trump alone, as the failure to protect the border would have a detrimental effect on the entirety of the Republican party as well.

“That’s the end of us if we give in on this issue as Republicans,” Graham said. “I hope Mitt Romney and everybody else knows this is a fight worth having.”

Trump and the Republicans are in for a serious fight as the Democrats have vowed to resist any funding for a border wall, even at the cost of an indefinite government shutdown.

At this time, Democrats are even refusing to listen to security briefings, instead focusing on their own agendas including ending the government shutdown, likely in an attempt to continue to paint Trump as at fault for it.