The road to the Republican presidential nomination is really just a two candidate race between billionaire businessman Donald Trump and Sen. Marco Rubio, House Majority Leader Kevin McCarthy told CNBC on Monday.

"I give Trump about a 50 percent chance of becoming the nominee. I give Rubio about a 35 percent chance," McCarthy told "Squawk Box." He said Sen. Ted Cruz had only an outside chance.

"I thought Cruz [had] had a very good chance of winning the nomination," he added. "But I don't see the math working out for him [now] that he didn't win South Carolina."



McCarthy, R-Calif., compared the Trump phenomenon to the GOP dynamic that swept actor Arnold Schwarzenegger into the governor's office in the Golden State's 2003 recall election.

"The momentum when Arnold Schwarzenegger ran for governor — I traveled with him — it was different people coming into politics [than] before and everybody thought that couldn't happen," McCarthy said.

"It's kind of ironic that they took Arnold to replace Trump in 'The Apprentice,'" McCarthy said. NBC — which along with CNBC is owned by Comcast — announced in September that Schwarzenegger would take over for Trump on the reality show.

McCarthy said politics as usual won't fly these days. "It is different environment and a different time," he said. "The country is so fed up with everything that has happened. They want to clean the slate."

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Trump takes the weekend win in South Carolina and the victory earlier this month in New Hampshire to Tuesday's Nevada caucus, and most importantly to next week's Super Tuesday contests, featuring primaries in Cruz's home state of Texas, Virginia, and many others.

"I think this thing will be over after March 15," when Rubio's home state of Florida holds its primary and the day states can award delegates on a winner-take-all basis, said McCarthy. "Momentum matters in this situation."

Regardless of the outcome, McCarthy said, "I can work with anyone who comes out of the Republican side."

