Democratic moderates are gearing up to mount a campaign to block a former presidential candidate, Howard Dean, from succeeding Terence McAuliffe as chairman of the Democratic National Committee, arguing that his election to the top post would prevent the party from moving to the political center.

The fight over the chairmanship risks becoming acrimonious, with Democrats already engaged in angry exchanges over who is primarily to blame for last week’s defeat in the presidential election and heavy losses in Senate and House races.

Moderates maintain that the party is increasingly out of touch with the values of mainstream America, and liberals are arguing that the party made a mistake in failing to nominate the former Vermont governor for president.

Dr. Dean, whose anti-war campaign for the presidential nomination imploded at the start of the winter primaries, indicated Monday night that he is pondering whether to pursue the chairmanship.

Liberal allies are urging him on, including a former Democratic national chairman, Steve Grossman.

“Howard is a voice of political empowerment, and that to me is important – for the Democrats to get their sea legs back as quickly as possible, to get beyond the disappointment of the last week, and to believe there is a bright future ahead for the Democratic Party,” Mr. Grossman, who was national chairman of Dr. Dean’s campaign, said.

Dean supporters point to the former governor’s skill at energizing the party’s rank-and-file and his innovative use of the Internet to raise money and generate support for his campaign.

“He would be a passionate spokesman for the Democrats, but also would be able to continue to revitalize participatory politics that is needed to grow the party,” Mr. Grossman said.

Party moderates, however, are already raising a hue-and-cry. With Dr. Dean in the top national party post, any attempt to rethink the Democrats’ big party orthodoxy would be hindered, they argue.

Speaking on CNN, an outgoing Democratic senator from Louisiana, John Breaux, warned that Dr. Dean is the wrong man for the job. “We’re going to have to move to the center,” Mr. Breaux said.

“There’s nothing wrong with that,” he added. “We can keep the base in by having good, solid Democratic ideas. But you’d better know how to expand them. Otherwise you’re going to be a party that loses elections. We’ve lost three in a row now. And I think moving to the center is where the answer is.”

Such remarks are dismissed by liberals, who say the Breaux prescription would transform the party into being Republican-lite.

In a speech in Albany this week, Dr. Dean warned the party against moving to the center. “We’re not retreating. We’re not giving up,” he said.

The roughly 240 members of the national committee will elect a new chairman early next year. Leading candidates include a former Clinton aide, Harold Ickes; strategist Donna Brazile, who ran Vice President Gore’s 2000 presidential bid; Governor Vilsack of Iowa, and Governor Warner of Virginia.

President and Senator Clinton, who maneuvered Mr. McAuliffe into the chairmanship four years ago, have remained silent about who should succeed to the post.

Party insiders said that Dr. Dean would not be the Clintons’ preference and that Mr. Ickes, a former Clinton deputy White House chief of staff, apparently has their support. “Senator Clinton needs a loyalist there for a possible presidential run in 2008,” a senior Senate Democrat told The New York Sun.

Southern Democrats are also pushing former Rep. Brad Carson of Oklahoma, who lost a Senate bid last week to Republican Tom Coburn. Mr. Carson, who received the endorsement of the National Rifle Association, ran as a moderate.

While acknowledging that he would be a longshot, the chairman of the Oklahoma Democratic Party, Jay Parmley, said Mr. Carson is exactly the kind of politician the national party should be turning to. “We need a moderate and a conservative to lead us into the midterm elections,” he said.

Speaking of the chairmanship, a Carson aide said the two-term congressman “feels the likelihood of that is not very real.”

The former Gore campaign manager, Ms. Brazile, is apparently positioning herself to appeal to centrist Democrats. In a column in yesterday’s edition of the Capitol Hill newspaper Roll Call, Ms. Brazile argued the party’s old orthodoxies have to be reappraised.

“There’s no question that it’s time to rebuild America’s oldest political party brick by brick,” she wrote. “The Democratic Party must lay a new foundation and stop spending its political capital defending old programs and initiatives. We must reclaim the mantle of the party of mainstream values.”

The choice of who should be the party chairman is intertwined with an internal debate about whether to adopt a strategy of accommodation or defiance on Capitol Hill in the face of the Republican sweep.