Washington ? The anti-war movement, which has been gathering support in recent months, will get a major test of strength Saturday as organizers hope to convene the largest peace rally in the nation’s capital since the Vietnam War.

Small demonstrations have been common since the Bush administration began contemplating war with Iraq nearly three years ago. But throughout the summer, support for the conflict, as measured by various polls, has dropped, and peace activists hope a large demonstration of opposition at Saturday’s event will show that the movement has turned a corner.

“It’s becoming clear to everyone that not only was this war based on a false pretext, it is not winnable,” said Brian Becker, national coordinator for the ANSWER Coalition, one of two umbrella groups organizing the rally. “The anti-war sentiment is now the majority.”

In August, “Peace Mom” Cindy Sheehan attracted significant attention with her vigil outside President Bush’s ranch in Crawford, Texas. Insurgents have killed huge numbers of Iraqi citizens in recent months and the death toll of American troops is approaching the 2,000 mark. With no immediate end to the war in sight, high gasoline prices and the government’s much-criticized response to Hurricane Katrina, Bush’s overall approval ratings have fallen.

A CNN/USA Today/Gallup poll released this week said 63 percent of Americans support the immediate withdrawal of “some or all” of the U.S. troops in Iraq.

Saturday’s “Bring the Troops Home Now” rally is the anti-war groups’ first opportunity to demonstrate that this general dissatisfaction can produce a tangible statement and that significant numbers of protesters are willing to travel to Washington to show their frustration.

But Bush will not be there to witness the protest. He traveled Friday to Colorado to monitor Rita’s progress at the U.S. Northern Command in Colorado Springs.