ABC News' Michael Falcone reports:

TROY, Mich. - In his campaign stump speeches, Rick Santorum often deploys a famous Ronald Reagan line, saying that he is the candidate of "bold colors" not "pale pastels," to show why he would offer the clearest contrast to President Obama.

On a chilly Saturday morning in Michigan, Santorum used some of those "bold colors" to paint Mitt Romney, his main rival in the primary here, as an elitist, inconsistent, liberal-in-Republican's-clothing, unexciting candidate.

"Every time we've run a moderate, we've lost," Santorum warned. "Every time we've run a conservative - a complete conservative on all the issues, I might add, national security, culture and economy - we've won."

On Romney's home turf, Santorum cast himself as the blue collar candidate in the race. He even highlighted the fact that his immigrant grandfather worked in Michigan for two years before leaving for the coal mines of Western Pennsylvania.

"I don't come from the elite," Santorum said. "I worked my way to the success that I have and I'm proud of it. Elites come up with phony ideologies and phony ideas to rob you of your freedom."

At a forum sponsored by the conservative group, Americans For Prosperity, he took particular umbrage with Romney's newly-announced tax plan, which would scale back deductions and exemptions for the richest Americans.

"I never thought that a Republican presidential candidate would adopt the verbiage of Occupy Wall Street," Santorum said.

Santorum, who opposes all government bailouts, blasted Romney's willingness to support the Wall Street bailout but not the automobile bailout.

"Why do you pick one and not the other?" he asked.

As he does everywhere he goes, Santorum pledged to be a "strong, consistent conservative."

When it comes to Romney, however, Santorum warned: "what you see" is not "what you get." Inviting the crowd to "imagine" what kind of candidate the former Massachusetts governor would be in a general election.  

In a nearly one hour policy address Friday night in a Detroit suburb, Santorum focused largely on what he views as the failures of the Obama administration. At his Saturday morning speech to a ballroom full of conservative activists, the former Pennsylvania senator took aim at President Obama's hope that every American will go to college.

"What a snob!" Santorum said.

"If you want big things to happen then you have to elect somebody and nominate somebody who can draw the clear contrast with President Obama," he said, appealing to the audience not to nominate someone - Romney - whose "own party isn't excited about campaigning for."

Receiving a standing ovation at his last public campaign event in the state on Saturday before departing for Tennessee, he told voters: "You have an opportunity here in Michigan to shock the country."