On the eve of his official campaign kickoff, Fred Thompson's campaign strategy is shifting dramatically.

The former Tennessee senator on Wednesday was set to appear on "The Tonight Show With Jay Leno" and was expected to make his official entry into the race on Thursday.

By doing so, Thompson was skipping a Republican debate — sponsored by FOX News — and instead planned on running a campaign ad during the debate.

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He later was expected to follow up the television ad with a longer Web video.

The moves mark a stark contrast to what earlier campaign officials had planned and advised him to do and give another reason for why Thompson appears to be losing his core of original supporters at a quickening pace.

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More resignations of Thompson's original core — "Fred Heads" — were expected in coming days, which could leave Thompson without any of his original supporters who joined him in March.

Thompson's campaign events and strategy for Wednesday and Thursday are markedly different than what had been under development since March and finalized just last month.

For instance, when Thompson appeared on Leno's show in June, several senior campaign staffers said that Thompson would "never return to Hollywood" for his campaign announcement, citing that that was how Republican candidate John McCain kicked off his campaign, which is now in the doldrums.

And the staffers also swore off a Web video announcement, the way Democratic candidate Hillary Clinton notified her base.

The plan had been to launch in Nashville and head to New Hampshire and Iowa.

One month ago, Thompson had a speech ready and the campaign had the original home of The Grand Ole Opry — The Ryman Auditorium — on hold with a planned announcement for Sept. 4.

The speech had been written, but two weeks ago new Thompson campaign manager Bill Lacy tossed it out. He replaced the speech with the video announcement and changed plans to skip the FOX debate.

The video remarks were written largely by Spencer Abraham, a former one-term Michigan senator and former Bush administration energy secretary.

Instead of running a "new kind of media strategy" it's now "pretty corporate" according to insiders.

While most of the original supporters have been fired or have left, two remaining sources say they will be quitting shortly, with new developments that recent hire Jim Mills is leaving.

Mills, a former FOX News congressional correspondent who joined Thompson's media team earlier this summer, was told he was being let go Friday, sources tell FOX News. He had been personally recruited by Thompson and his wife, Jeri, slightly more than one month earlier.

The sources say Lacy fired Mills and is looking to fill Thompson's team with former GOP staffers. Lacy ran Thompson's 1994 successful Senate campaign but later was fired as an ad consultant from the unsuccessful presidential campaign of Sen. Bob Dole in 1996.

Mills is only one of about a dozen who have left their jobs to join the Thompson campaign only to be released far sooner than expected. Sources reportedly are questioning whether they were misled about the campaign intentions.

And some of those who have left the campaign are saying that the missteps and turn-arounds are indicative of Thompson's inattentiveness and deep-seated disinterest or lack of motivation for the campaign.

There are more major resignations of founding Fred heads looming over the way the "new media strategy" was supplanted by a "corporate" and "predictable" approach. They also are protesting the way so many people have been treated by the candidate and spouse.

Tuesday Thompson's communications director defended the media strategy.

"We think one of the strongest weapons this campaign has is Fred Thompson's ability to connect directly with the public," said Todd Harris, Thompson's communications director. "We want to drive as much traffic as possible to the Web site."

While campaign insiders are less than optimistic of Thompson's approach, it might have a chance of working, said Tobe Berkovitz, the interim dean at Boston University's college of communications.

"That's the modern way to do it," Berkovitz said. "Especially if people are looking for something new on the Republican side. People have had plenty of time to look at Rudy or Mitt or McCain. So it makes sense for Thompson to march to his own campaign drummer."

FOX News' Carl Cameron and The Associated Press contributed to this report.