Pollster and political consultant Frank Luntz told "Special Report" Friday that President Trump's "tone is off," and it's hurting his bid for reelection.

"The undecided [vote] is so small, it's only six percent of the country and it's only in 10 or 11 states," Luntz told host Bret Baier. "So you're really looking at about two-and-a-half percent of Americans you're trying to influence. Ask them what they want.

"This is not core Trump voter. This is not core Biden voter. These are people who want empathy. They want understanding," Luntz went on. "The rhetoric, the language is different than what the president is communicating right now. And I think that that is significantly contributing to his numbers getting worse."

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Luntz argued that Trump's use of language, particularly in response to the protests that have gripped the nation following the death of George Floyd in Minneapolis police custody last month, makes undecided voters less likely to identify with him.

"The president talks about his own voters being 'warriors' because they're willing to stand up," Luntz said. "The problem with that is, an undecided voter, a swing voter, does not want to be a warrior. We all identify ourselves as hardworking taxpayers, so why not call them that?

"Another example, Donald Trump had the single best line of 2016 when he said at the Republican convention, 'I will be your voice,'" Luntz said. "But he doesn't communicate that right now. He doesn't say that. He doesn't go back to speaking on behalf of people. And so he's missing that segment of America that feels ignored or forgotten. And so, again, the challenge for him is he's not using the rhetoric of people who he needs to win over. He's using the rhetoric of people who he's already won over."

Luntz also urged Trump to acknowledge the ongoing threat from the coronavirus pandemic and claimed that presumptive Democratic presidential nominee Joe Biden is benefiting by not campaigning while Trump fails to connect with voters.

"He is unwilling to say that there is this concern and I'm not using the specific words," he said of Trump. "This is a tone as well. It's not just changing a word. It's doing something that he has not done and he's, up to this point been unwilling to do, which is in essence, what Bill Clinton did [and say] 'I feel your pain. I get it. I understand. And here's what we're doing for that.' He may think he's saying it, but he's not.

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"And Joe Biden is saying nothing at all. And that's why Biden is actually going up. If I were Joe Biden's consultant, I'd say stay in the basement. And I don't mean that as a joke," Luntz said. "You don't have to campaign ... And Donald Trump, if you're on TV every day for 60 or 90 minutes, your numbers are going down in the Fox poll, in the CNN poll, NBC, Wall Street Journal, Washington Post, some media publications that do not have an issue with Donald Trump and are not hostile to him. The numbers are going down."

Baier asked Luntz how to respond to Trump supporters who argue that the president's rhetoric won his the election in 2016.

"This is not 2016," Luntz said. "Joe Biden is not Hillary Clinton and it's not working this time."