Democrats will gain a majority in the House of Representatives in 2018 and attempt to impeach President Trump if Republicans fail to pass tax reform, Sen. Lindsey Graham, R-S.C., said Friday.

"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," Graham said on Fox News Radio's "The Brian Kilmeade Show." "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."

"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."

The House passed the Senate's fiscal 2018 budget on Thursday, paving the way for Congress to move forward with tax reform legislation. House Republicans plan to release their tax reform legislation on Nov. 1.

Editor's note: This story has been updated to correct the name of the Fox News Radio show.