A growing number of Democrats are signaling they won’t go along with the resolution. | AP Photos Obama losing Senate Dems on Syria

President Barack Obama’s push for military action in Syria is running into a serious problem — Senate Democrats.

Opposition is growing to a U.S. strike on Syria among Obama’s allies and former colleagues in his own party, a sign that there is a real chance that the White House could fall short of the 50 votes it needs to win in the Senate, according to several sources familiar with the situation.


Publicly and privately, an increasing number of Democrats are signaling they won’t go along with the resolution, at least not right now. While just six Senate Democrats have publicly announced their opposition, that number could increase dramatically in coming days, Democratic sources say.

There is still time for Obama to turn things around, especially as he personally leans on senators for support. He is coming to Capitol Hill Tuesday to address Senate Democrats and Senate Republicans at their party lunches. The president will also give a televised address to the nation on Tuesday night.

( PHOTOS: Syria: Where politicians stand)

But a mass defection among Senate Democrats could force the White House to turn to Republicans to push the Syria resolution through the chamber. That scenario seems unlikely to work given the scant support among congressional Republicans so far for “limited, proportional” strikes against the regime of Syrian President Bashar Assad over the alleged use of chemical weapons during an Aug. 21 attack in the Damascus suburbs.

And Russian proposal to put Syrian chemical weapons under international control could change the calculation — and timing of any votes — in the Senate, as well.

( WATCH: Timeline of Syria crisis response)

Yet on Monday, six senators — Republicans Lamar Alexander (Tenn.), Johnny Isakson (Ga.), Mike Enzi (Wyo.), Roger Wicker (Miss.) and Roy Blunt (Mo.), as well as Democrat Heidi Heitkamp (N.D.) — all came out against the Syria resolution, while Democrats Barbara Mikulski (Md.) and Martin Heinrich (N.M.) announced they’d back it.

In addition, a number of other Democrats are officially undecided, and the White House fears they may vote against the measure. These include Sens. Jon Tester of Montana, Elizabeth Warren of Massachusetts, Tim Johnson of South Dakota, Mary Landrieu of Louisiana, Richard Blumenthal of Connecticut and the independent Angus King of Maine.

( PHOTOS: Scenes from Syria)

“This is going to a be a very, very tough vote,” said a top Senate Democratic aide. “I’m not sure the president can win it.”

Senate Majority Leader Harry Reid (D-Nev.), a close Obama ally, is expected to push hard for the Syria resolution, as are other top Senate Democrats. Yet in a bad sign for the White House, a large number of Democrats remain unconvinced, concerned about public polls — as well as the streams of letters, phone calls and emails pouring into their offices — showing a large majority of the American public is opposed to a U.S. military intervention in Syria.

Obama himself would not predict whether he can get congressional backing for the Syria resolution during a series of TV interviews on Monday night.

“I wouldn’t say I’m confident,” Obama told NBC News. “I’m confident that the members of Congress are taking this issue very seriously and — and they’re doing their homework, and I appreciate that.”

( Also on POLITICO: President Obama: Strikes on hold if Assad turns over weapons)

With fears growing that his own party could reject the use-of-force resolution, Obama’s lobbying campaign is stepping into high gear. At the White House on Monday evening, nearly half of the Senate Democratic Caucus was invited to meet with Vice President Joe Biden, a day before Obama planned to make the trek down Pennsylvania Avenue. POLITICO reported that former Secretary of State Hillary Clinton has been calling members on behalf of the proposal, although one of the Democrats she contacted — Arkansas Sen. Mark Pryor — has already come out as a “no.”

Former Secretary of State Madeleine Albright and former Senate Majority Leader Tom Daschle (D-S.D.) have also been calling senators at the White House’s behest, said Democratic insiders.

The Senate is expected to hold a procedural vote later this week to open debate on the Syria measure, which was approved last week by the Foreign Relations Committee by a 10-7 vote. That cloture vote, which requires 60 backers, is expected to succeed as even senators who are expected to oppose the plan — like Senate Minority Whip John Cornyn — say they are prepared to open debate on the Syria resolution.

“I think [there] will be broad consensus to get on the resolution and offer amendments — and debate those — that’s what we’re supposed to do, and that’s what the gravity of this deserves,” Cornyn said.

Yet that’s the only thing that remains assured in the Senate on the Syria crisis. It’s unclear whether a second vote to end debate on the resolution — likely now to slide into next week — would garner the 60 votes necessary to move to a final up-or-down majority vote.

And with Democratic apprehension growing, it’s uncertain whether Obama could even hold a majority of the 54-member Senate Democratic Caucus to stand with him on the resolution.

Senate Majority Whip Dick Durbin (D-Ill.) said Democratic leaders are not weighing what to do if they cannot get the votes to pass the measure or cut off debate. He said the leadership’s focus now is on securing the 60 votes necessary to open debate on the resolution.

“We are just taking it one step at a time,” Durbin said on Monday, adding he had yet to gauge how his caucus felt about the merits of the resolution.

For now, the White House is urging Senate Democrats — even if they’re opposed to the measure — to at least vote to move to an up-or-down vote.

With a number of Democrats undecided leaning against the plan or downright opposed to the Syria resolution, it’s becoming increasingly clear that this is fast becoming one of the most important votes of the Obama presidency.

Another Democratic leadership aide said, “Not a lot of margin for error, but not time to freak out yet.”

Over the past few days, a number of Democrats have come out against the Senate resolution to allow military action in Syria within 90 days and ban ground troops. They include Heitkamp, Pryor and Sens. Joe Manchin (W.Va.), Brian Schatz (Hawaii), Chris Murphy (Conn.), and Tom Udall (N.M.).

Also undecided are Sens. Tammy Baldwin of Wisconsin, Max Baucus of Montana, Mark Begich of Alaska, Tom Harkin of Iowa, Mazie Hirono of Hawaii, Ed Markey of Massachusetts, Jeff Merkley of Oregon and Sheldon Whitehouse of Rhode Island.

At this time, GOP and Senate aides predict only about a dozen Senate Republicans would vote for a Syria proposal, meaning the White House can’t turn to the minority party for support.

Even loyal Obama allies are harboring doubts.

Washington Sen. Patty Murray, a member of the Senate Democratic leadership, called it a “difficult vote” and declined to say whether she would support it.

“I’ve always viewed the decision to use military force with careful consideration and caution, and I am certainly doing that in this case. I’m going to take every advantage of the briefings and meetings that I have lined up for this week — and of course, I’m continuing to listen to the voices of my constituents back home,” Murray said.

If Obama and Reid were to lose Murray — the fourth-highest-ranking Senate Democrat, chairwoman of the Budget Committee and a former chairwoman of the Democratic Senatorial Campaign Committee — they would also most likely lose her fellow Washington state Democrat, Sen. Maria Cantwell. And rank-and-file Democrats would feel more confident in bucking Reid and other party leaders if Murray was opposed.

Others on the left were more direct in their opposition.

Liberal Sen. Bernie Sanders (I-Vt.), who caucuses with Democrats, said he is “very, very concerned” that the resolution would lead to a “deeper [U.S.] involvement in Syria.”

“Ninety-five percent of my constituents have indicated to me in emails and phone calls that they do not want to see the United States getting involved in a bloody and complicated civil war in Syria — and that certainly has some influence on me,” Sanders said Monday.

And some moderate Democrats, like Heitkamp, are also voicing opposition.

Despite participating in a number of classified briefings, including one with Biden at the White House last week, Heitkamp said Monday that she had “serious concerns” and would not support the resolution.

“After doing my due diligence, I believe we need an alternative path forward in dealing with the Assad regime,” Heitkamp said.

Despite sitting through multiple classified briefings, King wouldn’t say on Monday whether he believed a military strike in Syria would succeed. “I’m not going to comment on that. I haven’t made that decision.”

King, who said he would support opening debate on the Syrian resolution, said that he was hearing many concerns from voters back home — and was still undecided on how to vote.

“Oh yeah, I mean, that’s not news,” King said when asked about concerns raised by Mainers.