INDIANOLA, Iowa — Sarah Palin struck a populist tone and assailed corporate favoritism Saturday in a campaign-style speech to tea party activists. The Republican star visited the state that kicks off the GOP presidential race as the clock ticks down on her self-imposed deadline to enter it.

She did not announce whether she will run for the White House. But the 2008 GOP vice presidential nominee did lay the rhetorical groundwork for an outsider campaign by advocating proposals aimed at addressing the nation's stubbornly high unemployment.

And in doing so, Palin set herself apart from President Barack Obama, a Democrat seeking re-election who is rolling out a jobs plan next week, and, in a veiled way, from some declared Republican presidential candidates.

"This is why we must remember the challenge is not simply to replace Obama in 2012. The real change is who and what we will replace him with," Palin said at a tea party rally in a rural area south of Des Moines. "Folks, you know it's not enough to change the uniform."

The audience of about 2,000 supporters from all over the country, dampened by heavy rains that quit shortly before the midday speech, erupted into chants of "Run, Sarah, Run!"

But Palin gave no response, and steered clear of any reference to a candidacy, even in jest as she has in the past, during her 40-minute speech.

"It would be a tremendous disappointment to a lot of people if she didn't run," said Mike Archambault, who traveled from Oregon to attend the rally.

Palin highlighted her two years as Alaska governor as an example of confronting powerful interests including the state's oil industry. She accused Obama and leaders in Washington of coddling corporations, at heavy cost to the taxpayers.

And while not naming any of her would-be GOP rivals, she also said other Republicans were guilty of repaying campaign donations with policy perks.

In recent weeks, media reports have pointed out instances in which people who have donated to Texas Gov. Rick Perry's campaigns have received appointments. That has left Perry vulnerable to criticism of corporate influence.

"There is a name for this. It's corporate, crony capitalism," she said.

Asked later if she was referring to Perry, she said all GOP candidates should be on alert.

"I want all of our GOP candidates to take the opportunity to kill corporate capitalism that is leading to this cronyism that's destroying our economy," Palin said, while in a crush of hundreds of supporters asking for autographs and posing for pictures.

Palin also said her remarks should not be construed as a campaign address, telling reporters: "It was a thank-you-tea-party-Americans speech."

Palin's appearance in Iowa came as she nears a late-September deadline for announcing her future political plans, if there are any.

Her Saturday appearance in Iowa and plans to headline a tea party rally Monday in New Hampshire, home of the first-in-the-nation primary, elevated the sense of urgency surrounding her.

Time may be running out for Palin to command the spotlight as she has throughout the summer, despite her coyness about a candidacy. There are three nationally televised debates for the declared GOP candidates, which are expected to shape the race in a way that could leave her behind.

Her speech Saturday stood out because after a summer of railing about the federal debt crisis, she switched gears and offered ideas she argued would lift the economy. She addressed jobs issue that declared candidates have only begun to tackle on the campaign trail.

She proposed expanding oil drilling and loosening regulations on it. She called for pared down business regulations. And she suggested eliminating the corporate income tax.

"It's not just fear of a double-dip recession, and it's not the shame of a credit downgrade," she said. "This is a systemic crisis due to failed policies and incompetent leadership."

Should Palin run, she may try to do so in an unconventional way.

Although she has drawn large crowds during two Iowa appearances within the past month, she has done none of the political spadework other presidential contenders have such as meeting with key party activists and officials.

Meanwhile, Republican candidates who are also popular with the tea party, including Perry and Minnesota Rep. Michele Bachmann, have emerged as contenders for the nomination. And Mitt Romney, the former Massachusetts governor, now is making a play for tea party support.

While Palin remains popular with tea party activists, her popularity with rank-and-file Republicans has dropped sharply.