Republican presidential front-runner Donald Trump's favorability ratings have declined substantially in the wake of the second GOP primary debate, a trend that, if it continues, could leave the real estate mogul with his lowest ratings ever, according to a Gallup analysis. At the same time, Trump's closest Republican competitor, retired neurosurgeon Ben Carson, has seen his ratings steadily increase.

Gallup looked at the seven days after the Sept. 16 debate, and found that Trump's net favorability ratings among Republicans is now just 21 percentage points, down from 32 percent in late August.

Actor and comedian Mel Brooks recently told USA Today that the world of comedy would be devastated if Trump, whose overall lead has decreased since the debate, were to fail in his presidential bid.

"If Donald Trump quit the race it would be the collapse of comedy," said Brooks, who takes on a grandpa vampire in the new movie "Hotel Transylvania 2."

"Trump means a great deal to comedy. You gotta keep him in right to the end."

He added: "We are so dependent on what he does, that he's needed. What would Kimmel and Conan and Colbert do? What would they do without Trump? They're in a lot of trouble without him."

Former President Bill Clinton, however, thinks that Trump could actually win the nomination.

"He's a master brander," Clinton told CNN's Fareed Zakaria on Saturday. "And when you've got a lot of people running, and people are trying, got to make distinctions, being able to put a personal stamp on it so people identify who you are, certainly counts for something, at least in the beginning."

When Zakaria asked Clinton if he thinks Trump could win, Clinton said "I think so."

While Trump's favorability ratings have been plummeting, Carson, the most favorable candidate in the whole GOP field, has seen his new favorability ratings go from from 50 percent in late August to 58 percent today, according to Gallup.

"For the seven days since the Sept. 16 debate, Carson's average net favorable image is even higher at +63," writes Gallup. "This period of time includes several days since his Meet the Press appearance on Sunday, Sept. 20. It is too soon to measure the long-term impact of his controversial comments on that program about voting for a Muslim for president, but the data show no evidence of a downturn so far."

Carson's name recognition has risen dramatically, too. In late July, some 47 percent of Republicans said that they knew enough about him to rate him, compared to the 74 percent who say the same today.

Kanye West even endorsed Carson in a recent interview with Vanity Fair, calling him the "most brilliant guy."

"As soon as I heard [Ben] Carson speak, I tried for three weeks to get on the phone with him. I was like this is the most brilliant guy," West said, as HNGN previously reported.