Early indications are that moderates from both major political parties could be vulnerable in this year's U.S. congressional midterm elections.
A fierce battle for control of Congress is expected this November and moderate candidates are already paying a price in the highly charged partisan environment.
In one primary race, Senator Joseph Lieberman, a leading Democratic moderate, lost to fellow Democrat Ned Lamont, in large part because of Democratic anger over Lieberman's support for President Bush on the Iraq war.
In Michigan, moderate Republican Congressman Joe Schwarz lost a primary battle to a more conservative candidate.
Political expert Norman Ornstein of the American Enterprise Institute says the focus of this year's elections is motivating the core supporters in both major political parties.
He spoke on C-SPAN television.
"The bases of the parties are mobilizing, more and more, and they are forcing people who come closer to the middle out of this process," he said. "There has really been a collapse of the [political] center in Congress. The Democrats have become more homogeneous and moved left. The Republicans have become more homogeneous and moved right."
The political stakes are high because many Democrats believe 2006 is their best chance to win back control of one or both houses of Congress since Republicans took over in 1994.
Democratic political strategists want to make the Iraq war the central issue in the campaign, hoping to take advantage of public unhappiness over the war that is reflected in opinion polls.
Harry Reid of Nevada is the Senate Democratic leader.
"We all agree there should be a change in the course of the war," said Mr. Reid. "We all agree that there should be a redeployment starting sooner rather than later."
Republicans are also gearing up for a tough fight in November, well aware that dissatisfaction over Iraq, high gas prices and President Bush could all work to the Democrats' advantage.
The president's top political adviser, Karl Rove, says Republicans will look to emphasize the administration's record in the war on terror.
"We are going to be just fine in the fall elections and we are going to be fine, because we stand for things that are important," said Mr. Rove. "We stand for strong national defense abroad and victory, complete victory, in the war on terrorism, which involves victory in Iraq."
Some moderates worry that the emphasis on sharpening differences between the parties will disappoint centrist and independent voters who reject the extreme wings of both parties.
Hamilton Jordan served as President Jimmy Carter's White House chief of staff.
He is now involved in a centrist effort called Unity '08 that seeks to offer a bipartisan presidential ticket in the next presidential election.
"We are people that are not satisfied with the current political system, not satisfied with the status quo and are working to offer the American voters an alternative in 2008," said Mr. Jordan.
Some political analysts warn that centrists or self-described moderates may find themselves shunted aside this year in the closely contested battle for control of the Senate and House of Representatives.
Thomas Mann is an expert with the Brookings Institution in Washington.
He says so-called tidal wave elections, when one party scores huge gains at the expense of the other, often have negative consequences for political moderates.
Mann says it last happened with the 1994 congressional elections that gave Republicans majorities in both the House and Senate.
"When Republicans swept into power, the most vulnerable Democrats were the conservative and moderate Democrats representing Republican [leaning] districts," said Mr. Mann. "And so when you have these tidal wave elections, you end up sweeping out those who have operated more toward the political center."
Some of the most closely watched races this year involve Democratic challenges to Republican moderates in Connecticut and Pennsylvania.