"It is amazing how across-the-board the opposition is. It's not just one group of people, it's all people from different, varied constituencies who are against the war," said Leslie Cagan, the national coordinator for United for Peace and Justice, an anti-war organization. "The sentiment is bigger now more than ever, there are more people against the war."

This anti-war voting bloc, a diverse group ranging from those who support an immediate withdrawal from Iraq to those who oppose President Bush's handling of the war, will again be critical to Democratic candidates' success in the 2008 presidential election as it was in the 2006 midterm elections that swept Democrats to power in Congress.

"In Kansas, Montana — solidly red states — incumbent Republicans lost to Democrats who are now clearly in office because of the public's revulsion with the war and Bush's policies," said Kevin Martin, executive director of U.S. Peace Action, a group founded to promote peace and nuclear disarmament in 1957.

These activists credit Democratic political gains in Western states and their taking control of Congress as directly tied to the issue of Iraq. A claim they are now using to push Democratic candidates to be more clearly opposed to the American presence in the war-torn nation.

Since the U.S.-led invasion in March 2003 and the toppling of Saddam Hussein's regime soon after, popular support for the Iraq war has been in steady decline. At the start of the conflict, 83 percent of Americans expressed confidence in the war, according to a CNN poll taken in 2003. But that number dropped dramatically to 56 percent in 2004, and a March 2007 CNN poll revealed that just 35 percent of the country supports the conflict in Iraq.

As public support fell, the anti-war movement broadened beyond traditional peace and anti-violence groups to include organizations not typically associated with war-related activism, such as the American Historical Association and military personnel.

In February 2007, the AHA passed a resolution urging their members to do "whatever they can to bring the Iraq war to a speedy conclusion."

And groups of former and current military personnel have become some of the largest, fastest-growing, and most visible opposition groups, according to Cagan.

"Military families, Iraq veterans, and veterans of other wars have come out and opposed it. People who have been most directly touched by the war, that's been the most dramatic increase," she said.

A December 2006 poll of 6,000 military personnel, published in the Military Times, showed that only 35 percent of troops approve of President Bush's handling of the war, down from 63 percent in 2004. Thirteen percent of respondents said that the United States should not even be in Iraq.

Much like the broader anti-war movement, these veterans' groups hold differing opinions on how to handle Iraq.

Some, such as the Iraq Veterans Against the War, call for an immediate withdrawal. Others, such as VoteVets.org, an organization founded by former Army Capt. Jon Soltz, who worked on Democratic Massachusetts Sen. John Kerry's 2004 presidential race, are opposed to President Bush's policies in Iraq and concerned about the war's implications on the domestic front.

"We're not a traditional anti-war group," said Soltz, adding that VoteVets.org is associated with another anti-war and staunchly liberal organization MoveOn.org. "We feel that the Iraq war is detrimental to national security."

Despite the differences, he said his group shares the same focus as other organizations.

"I think when you talk about getting out and anti-escalation, it's really an opposition to the president as a whole," he said. "You have people who are pacifists to people who are in the military uniting against the administration's policies."

A February 2007 poll taken by the Washington Post showed that the Iraq war was the single most important issue to Democrats when choosing a presidential candidate.

And many Democratic presidential contenders are responding, hoping to court these voters. Former North Carolina Sen. John Edwards has repudiated his 2002 vote to authorize military action in Iraq; Illinois Sen. Barack Obama, who was not in Congress when it voted to authorize military action, has reiterated that he has been against the war since its inception; and Ohio Rep. Dennis Kucinich continues to demand that Congress cut off funding for the war.

In recent weeks, Obama has received the most support from anti-war voters. Obama led an April poll by MoveOn.org surveying thousands of members following a virtual forum on Iraq.

Sen. Hillary Clinton, D-N.Y., has lagged behind in surveys of anti-war voters and has repeatedly been questioned about her refusal to apologize for her 2002 vote authorizing the war. But Clinton's campaign thinks that her steadfastness will prove to be an asset.

"She is in a box now on her Iraq vote, but she doesn't want to be in a different, even worse box — the vacillating, flip-flopping Democratic candidate that went to defeat in 2000 and '04," one Clinton adviser told the New York Times in February. "She wants to maintain a firmness, and I think a lot of people around her hope she maintains a firmness. That's what people will want in 2008."

With the first primary elections still almost a year away, some anti-war organizations are wary that the issue will remain as significant in the coming months.

"Right now it's easy for candidates to address the movement. Bush's approval rating is low and it's easy for Democrats to be seen as anti-war," said Martin. "If the intensity and fervor is lost, some of the progress might be countered. They can't take the anti-war vote for granted."

Candidates, especially current officeholders, will have to not only talk about ending the war, but make some tangible progress over the next year in order to maintain support of the anti-war constituency.

"What's important for people is what candidates are going to do as their plan to end the war," said Cagan. "Those people who happened to be in the Senate are going to be scrutinized. People are going to be pushing the candidates into answering questions about their actions."