IMPEACH BUSH

WASHINGTON (CNN) -- When American troops crossed into Iraq in 2003, nearly three out of every four Americans backed President Bush's decision to use military force to topple the regime of Saddam Hussein.

Four years and more than 3,200 U.S. deaths later, less than one-third of Americans support the war, according to the latest CNN/Opinion Research Corporation poll.

Republicans and Democrats see the conflict much differently, according to the poll. More than 90 percent of Democrats oppose the war, compared to 24 percent of Republicans. In contrast, four years ago, 55 percent of Democrats and 91 percent of Republicans supported the war.

That partisan divide stands in stark contrast to the nation's last bitterly divisive war, a generation ago in Vietnam.

In 1971, when public opposition to the war in Vietnam was about the same as today's opposition to the Iraq war, both Democrats and Republicans opposed the conflict in nearly equal percentages. At the time, Republican Richard Nixon was in the White House, managing a war he inherited from the Democratic Kennedy-Johnson administration.

This time around, Bush finds himself living with the fallout from his own decision to invade Iraq. Most of his fellow Republicans remain supportive, but his policy has very little backing among Democrats.

The largest drop in support for the Iraq war came in the first year, after U.S. troops were met by a stubborn insurgency and failed to find any weapons of mass destruction.

By March 2004, only 48 percent of the American public supported the war, compared to 72 percent around the time of the invasion. The support numbers continued to drop, to 47 percent in 2005, 40 percent last year and, now, 32 percent.

There is one encouraging sign in the poll numbers for Bush -- the number of people who believe the United States is making progress in Iraq has risen to 29 percent, compared to 24 percent in January, when Bush announced his plan to add U.S. troops to try to help Iraqis get a handle on sectarian violence.

However, twice as many Americans believe the United States is losing ground compared to the number of people who think progress is being made.