Democratic presidential candidate John Kerry (search) promises to stand up for hard-working people against an "economy of special privilege" as he fine tunes the arguments he'll take to voters before next week's Iowa caucuses (search).

"To me this is a matter of principle," the Massachusetts senator said in remarks prepared for delivery Wednesday. "Democrats should stand up for everyday Americans who work hard, hope for the future and face extraordinary challenges everyday."

In the speech, Kerry criticizes President Bush for policies that he says favor the wealthy and powerful. And he pulls together previously announced proposals — ranging from new protections for pensions, restrictions on lobbyists and setting limits on executive pay — into a single package framing his candidacy.

Kerry's campaign billed the speech at a college in Davenport as defining his candidacy in the run-up to Monday's caucuses, considered tight and volatile. Most polls have shown former Vermont Gov. Howard Dean (search) and Missouri Rep. Dick Gephardt (search) bunched together tightly atop the field of Democratic contenders, with Kerry and North Carolina Sen. John Edwards (search) fighting for third place.

Virtually all surveys have shown a large number of undecided voters, with an even larger group willing to change their mind in the closing days, lending a sense of uncertainty to the race.

Kerry was using his speech to sound a populist theme, and underscore his core campaign theme that his history as a Vietnam War hero gives him credibility to challenge Bush in a campaign thought likely to center around issues of national security.

At the heart of the package is a disagreement Kerry and others have waged with Gephardt and Dean over taxes, with critics arguing that both rivals favor increases in middle-class taxes by proposing to repeal Bush's tax cuts.

"While we must repeal the Bush tax cut for the wealthy, I will fight — and I ask you to join me in fighting against — proposals to increase taxes on the middle class," Kerry said in the remarks, which were obtained by The Associated Press. "I disagree with those in my own party who are so mad at George Bush that they want to take it out on working families in Iowa by raising their taxes an average of $2,000 a year."

That's a particular swipe at Dean, who critics say runs a campaign fueled by anger. "I ask you to vote for answers not anger," Kerry says.

At issue are differences among the Democratic rivals over tax cuts Bush pushed through Congress. Virtually all the Democrats argue that portions of the tax cut — particularly for the wealthy — should be eliminated, with the money being used for programs like expanding health care.

Dean and Gephardt go further, arguing for ending all the tax cuts, including portions that mainly benefit middle-class taxpayers such as a child care tax credit. Dean argues that it's urgent to begin balancing the federal budget and he seeks a health care expansion, all financed by repealing the tax cuts. Gephardt also calls for eliminating the tax cut, and using the money to pay for his universal health care plan.

In his speech, Kerry says working Americans deserve "a government on their side that knows when to take sides."

"We need leadership and resolve to take on the special interests here at home and the experience and the judgment to lead America in a dangerous world in a perilous time," Kerry said.