On "Fox and Friends Weekend" today, Frank Luntz revealed that Hillary Clinton's poll numbers keep dropping, while Vice President Joe Biden, who hasn't even announced his candidacy, keeps gaining ground on the Democratic front-runner.

Luntz explained that if a candidate has poor favorability, if people aren't considering voting for him or her, then there is no way for that candidate's numbers to go up.

"Hillary is at 38 percent favorability. If she ends the election on that, and she were ever elected president, it would be the lowest favorability that anyone that has ever been elected into presidency in American history [with]," Luntz said.

He added that no successful presidential candidate has had more than a half of the country feel unfavorably towards them, as Clinton does.

"Her numbers compared to Joe Biden: She keeps dropping, Biden keeps rising. If he decides to run, he’s going to make a race of it," Luntz said, noting that Biden has the highest favorability numbers of any possible 2016 candidate.

"If I were Joe Biden’s strategist, I would be telling him, 'Get in the race and make sure you participate in that first presidential debate.' That’s coming up on October 13."

Watch more above.

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