A senior strategist at the Republican National Committee said Friday that Hillary Clinton's attempt to brand Donald Trump and his supporters as racists shows the presidential race is getting tighter.

"Literally, how desperate is she?" Sean Spicer told MSNBC's Stephanie Ruhl. "She put out an ad yesterday trying to link white supremacists to Donald Trump. This is a new low."

The ad, released by the Clinton campaign on Thursday, featured footage of Ku Klux Klan members endorsing Trump. A black pastor belonging to the Republican presidential nominee's evangelical advisory board later described the ad as "disgusting."

"The video they put out yesterday was unbelievably over-the-top," Spicer said, adding that "the idea that they have gone to that level of desperation shows that they know that the polls are closing and they know that their stale, status-quo message isn't resonating with the American people."

Clinton also delivered a speech about Trump and his supporters in Reno, Nev., on Thursday, during which she accused her Republican opponent of "taking hate groups mainstream" and running a campaign "built on prejudice and paranoia."

Still, Spicer declined to condone Trump's charge that Clinton is a "bigot."

"Do you think Hillary Clinton is a bigot?" Ruhl asked him.

"No, I mean, I think some of the policies that she supported have not helped the African-American," Spicer responded. "But I think anybody who knows me, I just don't tend to use certain words, but again, I'm not ... That's something that I might personally say, no."

Spicer announced earlier this week that he plans to spend several days each week working with the Trump campaign inside its New York City headquarters beginning after Labor Day weekend.