The White House struggled on Monday to build momentum among lawmakers in Congress for plans to authorize the use of military force against Syria, as Senators from both parties announced they could not support such plans, while new polls showed strong opposition to the idea.

"I cannot support the current Senate resolution to authorize force at this time," said Sen. Heidi Heitkamp (D-ND).

"I will vote ‘no’ because of too much uncertainty about what comes next," said Sen. Lamar Alexander (R-TN).

"While I believe the use of chemical weapons is despicable and the world must take action to ensure that cruel dictators are not allowed to use such weapons without repercussions, at this time I cannot in good conscience support current proposals to take unilateral, military action," said Rep. Tim Walz (D-MN).

"I believe this strategy and the unknown response it may provoke are the wrong thing to do, and I will not support the resolution the President has asked for," said Sen. Roy Blunt (R-MO).

While the White House failed to get the votes of Senators like Heitkamp, Blunt and Alexander, there was also the danger that the President might lose the backing on some who have been counted as "Yes" votes, like Sen. Johnny Isakson (R-GA).

After an Isakson spokeswoman told me today that he was "undecided" on Monday afternoon, a few hours later, Isakson officially announced that he would vote against using military force on Syria over that nation's use of chemical weapons, saying that home-state voters are "skeptical" of U.S. attacks.

That was a big change in just nine days, since Isakson issued a statement on August 31 that seemingly left no wiggle room on where the Georgia Republican stood on Syria.

"I support the use of military action in Syria," Isakson said in a statement that is posted on his Senate web site.

If Isakson's statement didn't make some wonder about momentum running the wrong way on the White House, an hour after that, Senate Majority Leader Harry Reid delayed the parliamentary machinations needed to hold a first test vote on the Syria resolution, meaning there would be no Senate vote before Thursday at the earliest.

While Reid said he was sure he had enough votes to overcome any filibuster, others weren't so sure in the halls of Congress, making President Obama's speech to the nation on Tuesday night all the more important.

"President has a lot of work to do," one Senator told me late Monday night, adding that the current Syria resolution "would not pass today."