Sen. Lindsey Graham Lindsey Olin GrahamGraham: GOP will confirm Trump's Supreme Court nominee before the election Fox's Napolitano: Supreme Court confirmation hearings will be 'World War III of political battles' Grassley, Ernst pledge to 'evaluate' Trump's Supreme Court nominee MORE (R-S.C.) on Friday warned that if Republicans fail to deliver on their promise to reform the tax code, they'lll likely lose their majority in the House.

In an interview with Fox News Radio's Brian Kilmeade, Graham cast a successful vote on tax reform as vital to Republicans' survival in Congress following the failure of efforts to repeal and replace ObamaCare.

"Well, I think all of us realize that if we fail on taxes, that's the end of the Republican Party's governing majority in 2018," he said. "We'll lose the House, probably lose ground in the Senate. And President Trump has got a profile different from the party — there's kinda two or three different Republican Parties now, I guess. But we're all in it together."

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Graham also said that, if Democrats take back the House in 2018, they would soon move to impeach the president.

"I can't imagine how he could be successful with Nancy Pelosi running the House," he added. "They'd try to impeach him pretty quick and it would be just one constant investigation after another. So it's important that we pass tax reform in a meaningful way. If we don't, that's probably the end of the Republican Party as we know it."

Trump and congressional Republicans have vowed to pass tax reform quickly. GOP lawmakers moved closer to that goal on Thursday, when the House passed a budget resolution that had been cleared by the Senate last week.

That budget will allow the Senate to approve tax reform legislation with just 51 votes, meaning that they will be able to avoid a Democratic filibuster.

According to a Politico report, House Minority Leader Nancy Pelosi (D-Calif.) told Democratic lawmakers at a caucus meeting this week that Republicans would lose their majority in the House if they failed on their tax reform promise.