A sure sign that it's election season: Gov. Charlie Crist is changing again.

The populist Republican is trying to convince people he's a conservative now that his opponent in the primary for Senate, former House Speaker Marco Rubio, has cut considerably into Crist's lead in the polls with a conservative message.

In the most extreme example of Crist reinventing himself, the governor denied endorsing the $787 billion federal stimulus and put out a radio ad in October criticizing President Barack Obama for trying to spend his way to prosperity. Crist clearly did endorse the package in February, saying it would help re-ignite the economy.

Choosing or changing positions based on what's politically popular is nothing new for Crist. Whether it's abortion laws, oil drilling or even the politicians he associates with, Crist can be a political chameleon.

"I do see him as a populist because he does, sort of at the moment in time, reflect what people are thinking and then moves with the public," said Susan MacManus, a University of South Florida political science professor. "The true base conservatives think he's a Republican one minute and a Democrat the next."

So far it has worked. Crist has won his last three statewide races _ education commissioner, attorney general and governor. Next year, though, could be problematic. Populism works in good times, but in bad times voters want strong leadership, MacManus said.

It doesn't help that Crist's credibility has been hurt.

"Once you've had your credibility questioned it makes it easier for somebody to continue questioning and for the groundswell to begin, and I think that's what's happened with Crist," she said.

The governor was asked on CNN last month if he regretted endorsing the stimulus package. He answered, "I didn't endorse it. I didn't even have a vote on the darned thing."

Even if Crist never used the word "endorse," he literally embraced Obama during an event to push for the stimulus, wrote to Obama saying he supported the bill and called Florida's House members and senators to ask them to vote for it.

Does denying he endorsed the stimulus hurt his credibility?

"Well I hope not. I don't think so," Crist told The Associated Press.

He said he did support the stimulus and would do so again, explaining that he thought it was going to pass anyway and he wanted Florida to receive its fair share of the funds.

"Charlie has given everybody multiple reasons to question everything that comes out of his mouth, whether it's true or whether he'll change his mind from one day to the next," said Brett Doster, a Republican strategist who worked for Crist's 2006 primary opponent.

Doster also knows Crist has a history of political shifts.

"He's lived his political career in the ambiguous zone," Doster said.

For example, Crist says he's a conservative, but two years he was asked what that meant and he said, "I don't know. It doesn't really matter to me, if you want to know the truth."

While Crist was campaigning for governor, a Roman Catholic priest asked him if he would sign the same bill passed in South Dakota attempting to ban abortion. "Yes I would," Crist said without hesitation. Minutes after he left the event, he clarified his remarks to say he would sign such a bill only if there were exemptions for rape and incest victims. He later said he would rather change hearts, not laws.

Crist built up crossover political appeal by appearing with Democrats Robert F. Kennedy Jr. and former President Bill Clinton to promote clean energy, but he changed a yearslong opposition to oil drilling off Florida's coast after Republican presidential nominee John McCain said the nation needs more offshore drilling.

During the 2006 primary, Crist repeatedly praised Gov. Jeb Bush and said he would govern in the popular conservative's tradition. The day after the primary, Crist's campaign Web site took down its photos of Bush. And as governor, Crist has taken positions that are the opposite of Bush's, including Crist's efforts to expand Indian casino gambling.

Crist also associated himself with Bush's brother, President George W. Bush, when it was convenient, and dissociated himself from him when it wasn't. Immediately after the 2006 primary, Crist proudly stood with the president during a fundraiser that took in $3.3 million for the Florida GOP _ most of which was used to help elect Crist.

But the day before that November's election, he refused to join the president at a Florida event to rally Republican voters. At the time, the president's approval rating was low and he was only traveling to areas where his help was wanted. The White House was surprised and embarrassed when Crist said at the last minute that he wouldn't appear with Bush. Schedules had already been printed listing Crist as announcing him.

Now that Rubio is gaining ground and depicting Crist as a moderate, Crist says he has consistently been conservative.

"I don't change my stripes from day to day," Crist recently told a Republican crowd.