WEST PALM BEACH, Fla. – On a day that combined two campaigns into one, President Obama on Wednesday challenged Republicans to raise taxes on the rich as Republicans Mitt Romney and Newt Gingrich swiped at him on the economy and criticized each other over immigration.

With less than a week to go before Tuesday’s Florida Republican presidential primary, the polls suggested a tight race, although Romney and his allies seized a staggering advantage in the television ad wars. They have reported spending $14 million combined on commercials, many of them critical of Gingrich, and a total at least seven times bigger than the investment made by the former House speaker and an organization supporting him.

Obama’s political timeline was a different one, Election Day on Nov. 6. In a campaign-style appearance in Iowa, he demanded Congress approve a tax increase for anyone like Romney whose income exceeds $1 million a year.

“If you make more than a million dollars a year, you should pay a tax rate of at least 30 percent. If, on the other hand, you make less than $250,000, which includes 98 percent of you, your taxes shouldn’t go up,” he said after touring a manufacturing plant in Cedar Rapids and in a state he won in 2008 that was expected to be a battleground in the fall.

“This is not class warfare,” he said. “That’s common sense.”

As Obama surely knew, it was an offer Gingrich, Romney and the anti-tax Republicans in Congress are likely to find easy to refuse.

In remarks his aides billed as a rebuttal to the State of the Union speech, Romney said Obama “seemed so extraordinarily detached from reality, so detached from what’s going on in Florida,” where unemployment is 9.9 percent and the mortgage foreclosure crisis has hit particularly hard.

Gingrich was far harsher at an appearance in Miami.

“If he actually meant what he said, it would be a disaster of the first order,” Gingrich said of the president’s call for higher taxes on millionaires.

The former House speaker said the president’s proposal would double the capital gains tax and “lead to a dramatic decline in the stock market, which would affect every pension fund in the United States.”

“It would affect every person who has a 401(k). It would attack the creation of jobs and drive capital outside of the United States. It would force people to invest overseas. It would be the most anti-jobs single step he could take,” he said.

Romney has long led in Florida’s polls, but Gingrich’s upset victory last Saturday in the first-in-the-South primary in South Carolina revitalized his candidacy and raised questions about the former Massachusetts governor’s staying power.

Former Pennsylvania Sen. Rick Santorum is also on the ballot, as is Texas Rep. Ron Paul. But Santorum has been sinking in the polls as Gingrich rises, and Paul has indicated he intends to bypass the state to concentrate on caucuses elsewhere.

That gives Florida the feel of a two-man race, and Romney and Gingrich are treating it that way. A second debate this week is set for tonight in Jacksonville.