Just one day before voters head to the polls, Sen. Lindsey Graham is optimistic about Republicans' chances in the midterm elections, saying, "I've never seen Republicans more united."

Graham (R-S.C.) is on the campaign trail with Vice President Mike Pence, making closing arguments to voters in Montana and South Dakota.

"I think we're going to kick butt in the Senate, and the House is too close to call," Graham said on "Fox & Friends" Monday.

He said the last 30 days have been a "nightmare" for Democratic candidates in states that went for Trump in 2016, pointing to the booming economy, the controversy surrounding the confirmation of Supreme Court Justice Brett Kavanaugh and the migrant caravan that's headed for the U.S. border.

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He said the partisan fight over Kavanaugh -- who was accused of sexual misconduct by several women -- "brought out a different side of Lindsey Graham" and now he's "fighting back."

"The Democrats will do anything to win. They do not accept the fact that President Trump won," Graham said.

"We've got to keep the Senate and grow our majority to get these judges on the court," he added.

He said Democrats are still trying to undermine the results of the 2016 election, and it's going to hurt them in Trump states.

"I think we're going to have a hell of a night in the Senate. And I think the House is going to surprise a lot of people."

Watch more from "Fox & Friends" above.

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