So the groups that are organizing the demonstrations against the president’s strategy are also carrying out a sophisticated, well-financed lobbying campaign on Capitol Hill. Their behind-the-scenes efforts are intensifying, relying on tactics deployed in a cutthroat political race.

Americans Against Escalation in Iraq, a coalition of labor unions, MoveOn.org and other groups that have traditionally rallied against wars, has raised $1.5 million since it was formed two weeks ago. The group is singling out Republicans and Democrats who have spoken out against the war, but who have so far declined to pledge support for a resolution denouncing Mr. Bush’s plan to increase the number of troops.

Next week, the group intends to fly Iraq veterans to the home states of Republican senators who serve on the Foreign Relations Committee and voted Wednesday against the resolution condemning the administration plan, including Senators Norm Coleman of Minnesota and John E. Sununu of New Hampshire. Television advertisements are scheduled to be shown in some of the same states in an effort to apply pressure before the Senate vote on the resolution in early February.

If the United States Senate passes a resolution, non-binding or otherwise, that criticizes the commitment of additional troops to Iraq that General Petraeus has asked for and that the president has pledged, and if the Senate does so after the testimony of General Petraeus on January 23 that such a resolution will be an encouragement to the enemy, I will not contribute to any Republican senator who voted for the resolution. Further, if any Republican senator who votes for such a resolution is a candidate for re-election in 2008, I will not contribute to the National Republican Senatorial Committee unless the Chairman of that Committee, Senator Ensign, commits in writing that none of the funds of the NRSC will go to support the re-election of any senator supporting the non-binding resolution.

While Democrats have shown little reticence speaking against the president’s plan, there is little agreement on the next step. Next week, Senator Russell D. Feingold, Democrat of Wisconsin, is convening a hearing to discuss the ways in which Congress can begin blocking the financing for the war, an idea that remains deeply controversial inside the party.

“It’s a walk in the park right now to oppose the idea of this war. It’s also very easy to oppose the escalation,” Mr. Feingold said. “They are once again being too timid and too cautious.”