He is one of the last of the unabashed liberals, a Democratic stalwart with little patience for party regulars cowed by President Bush's soaring poll numbers.

"If it was the economy, stupid, in 1991 and 1992, it's the economy, stupid, in spades now," says Tom Harkin (search), a bespectacled senator who captured his fourth term in November.

What sets apart this partisan are status and geography. Harkin is the senior Democrat in Iowa, the first test of the presidential nominating season and a state that could help sort out the crowded Democratic field.

And Harkin, 63, won't be going along just for the ride. He has played a prominent part in past Democratic races for the presidency, and he is determined to shape the debate in this election.

Earlier this year, Harkin scheduled a series of "Hear It From the Heartland" forums that would provide the Democratic hopefuls a chance to make their appeals and answer questions from local activists. The 90-minute sessions began with Sen. John Edwards of North Carolina in April, continue with some of the nine candidates this summer and end with Sen. Joe Lieberman of Connecticut in September.

On Sunday, Howard Dean (search) has his moment in the Iowa spotlight.

Harkin, who established a political action committee to promote and pay for the forums, has guaranteed a good turnout, and more important, attendance by Iowa activists certain to show for the precinct caucuses Jan. 19.

"It gives him the opportunity to essentially be a kingmaker," said veteran Iowa Democrat Joe Shanahan.

Harkin easily could have sat on the sidelines this election cycle, choosing to rest after his tough fight to keep his seat against a challenge from Republican Greg Ganske in November. Harkin prevailed by 10 percentage points.

But it wasn't in his nature to pass on the 2004 presidential race.

"I want to get our candidates focused and get the debate started as early as possible so we don't end up out in the weeds somewhere," he said.

Elected to the Senate in 1984, Harkin has used his positions on the Senate Appropriations Committee and as ranking Democrat on the Agriculture panel to work closely with Republicans on various legislation. His most significant achievement was the 1990 Americans With Disabilities Act (search), which he sponsored.

A fervent backer of the energy source ethanol - an alcohol distilled from corn and mixed with gasoline - Harkin once sipped some at a Senate hearing to show it's safe.

On the political front, partisanship overshadows legislative compromises.

While Republicans and several Democrats cheered Bush after the Iraq war, Harkin argued the quick collapse of Saddam Hussein's government showed he was a "paper tiger."

The backing of this Iowa liberal will be crucial to the nine presidential candidates.

In 2000, then Vice President Al Gore faced what appeared to be a serious and well-financed challenge from Bill Bradley, and both courted Harkin. The senator, an also-ran from the 1992 president race, endorsed Gore months before the Iowa caucuses and turned his campaign machinery over to the Gore campaign.

So after the forums are over, the question is which Democrat will get his support.

"I think he's trying to find a candidate who can explain his ideas to the public," said Democratic activist Phil Roeder. "If he can't do that in a meeting hall in Des Moines or Mason City, it's going to be tough to do that a year from now against George Bush."