(Image Credit: Rainier Ehrhardt/AP Photo)

ABC News Amy Walter and Emily Friedman report:

CHANDLER, Ariz. - Just hours before he meets his main rival for the 20th - and likely final - debate of the primary season, Mitt Romney didn't even mention Sen. Rick Santorum during a speech this morning. Instead, he offered new details on his tax plan.

"I'm going to lower rates across the board for all Americans by 20 percent," Romney said.

"With regards to our tax policy, our growth with regards to our tax policy, there are a couple things I'd like to announce to you today," said Romney, speaking in a gymnasium at the Tri-City Christian Academy. "And in order to limit any impact on the deficit - because I don't want to add to the deficit - and also in order to make sure that we continue to have progressivity as we've had in the past in our code, I'm going to limit the deductions and exemptions, particularly for high income folks."

Romney said his plan to limit mortgage interest and charitable contributions deductions would not impact middle income families. Instead, he noted, he wants to "make sure the top 1 percent keeps paying the current share they're paying or more."

Romney tonight will debate fellow Republican candidates, including Santorum, who over the past week has defined himself as Romney's chief competitor. But during this morning's rally, Santorum's name wasn't mentioned, nor were there jabs at "Washington insiders" that have been a part of Romney's stump speech all week.

Instead, it was Romney's tax plan, and its contrast to Obama's plan, that filled the 15-minute speech.

"The president would take us in one direction, I'll take us in a different one," said Romney. "His plan in regards to jobs is very simple. He wants to raise taxes. That will kill jobs in this country."

"He's proposing today a corporate tax plan which I understand sounds like he's lowering taxes. But he's raising taxes, raises taxes on businesses by hundreds of billions of dollars," said Romney. "He's raising taxes on these companies that flow through - that pay taxes on individual rates. Raising taxes will kill jobs. My plan will create jobs. That's the difference between the two of us."

Ben LaBolt, a spokesman for the Obama campaign defended the administration's tax policies and criticized Romney's proposal.

 "The President has cut taxes on small businesses 18 times, provided every working American a tax break," LaBolt said.

Romney, he said, is "giving more tax breaks to millionaires and billionaires… and lowering corporate taxes without explaining how he would pay for them."

"For all that business experience Mitt Romney touts, it's odd that he didn't learn how to balance his own books," LaBolt said.