Her husband has already done three visits, but Michelle never found the time to sit down with Stewart. The interview will air after the second presidential debate — a night of politics and high ratings.

Michelle held her own against a more challenging Comedy Central host, the conservative/liberal firebrand Steven Colbert.  In April, she joined him for his hyperbolic, week-long Pennsylvania primary special, the “Doritos’ Spicy Sweet Pennsylvania Primary Coverage From Chili-Delphia – The City of Brotherly Crunch!”

Fox News is promoting Obama's Thursday appearance.

As Sen. John McCain accepts the GOP presidential nomination on Thursday night, his opponent will enter the “No Spin Zone.”

Yes, Sen. Barack Obama is headed for Fox News, in a bid for Republican votes, by appearing for the first time ever on Bill O’Reilly’s prime-time show. While McCain aims his acceptance speech at voters beyond his base, Obama will be talking to the bright red Republicans who watch O’Reilly’s highly rated show. In the last presidential election, a whopping 88 percent of Fox viewers voted Republican, while only 7 percent voted Democratic.

Obama’s appearance also caps an unusually long and rocky exchange with O’Reilly.

A senior aide to Obama said the controversial anchor “shoved” him during a February altercation in New Hampshire, when O’Reilly tried to confront the Illinois senator to demand he appear on the Fox program. “I’ve worked two [presidential] campaigns, and I’ve never had a member of the press lay hands on a staff member before,” said the aide, Marvin Nicholson, who travels with Obama. Then, at a secret June meeting with Rupert Murdoch, the owner of Fox, and Roger Ailes, who runs it, Obama aired his concerns about the network’s biased coverage and agreed to appear on O’Reilly’s show, according to new reports from Vanity Fair and The Washington Post.

Beyond O’Reilly’s show, Fox News has been under siege this election season by several liberal groups supporting Obama. The channel was shut out of Democratic primary debates, after Democratic activists and bloggers scuttled its attempt to host debates with the Congressional Black Caucus. More recently, Fox was rocked by allegations of anti-Obama bias and racial prejudice in campaigns by Color of Change, a netroots group focused on black issues and civil rights — that was the battle featuring the rapper Nas on the Colbert Report — and a viral video campaign by Brave New Films.

Obama’s exclusive appearance, however, shows that he’s willing to tap the Fox News for potential conservative voters — even as his supporters try to marginalize its political role.