Republican strategist Frank Luntz on Sunday criticized Republican presidential nominee Donald TrumpDonald John TrumpTrump suggests some states may 'pay nothing' as part of unemployment plan Trump denies White House asked about adding him to Mount Rushmore Trump, US face pivotal UN vote on Iran MORE's campaign, saying this election "should have been a slam dunk for the GOP."

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Luntz said on CBS's "Face the Nation" that Trump's campaign has been focused on the billionaire and his battles with "just about everybody."

"If he had stayed the voice and the vision for those people who have been left behind, this race would be a lot different than it is right now," he said.

Still, Luntz said he doesn't think the race is over.

He said there are enough people who are still undecided and noted Democratic presidential nominee Hillary ClintonHillary Diane Rodham ClintonHillary Clinton labels Trump coronavirus executive actions a 'stunt' What Trump got wrong by pushing coal Trump is fighting the wrong war MORE is under 50 percent support in many polls.

"But it requires a level of discipline that the Trump campaign has not had," he said. "This is about the voice of the voters, not the voice of Donald Trump."

Luntz continued to criticize the Trump campaign.

He said he has never seen a campaign with "less discipline" or "less focus."