(Kristoffer Tripplaar/Pool/Abaca Press/Corbis)

As President Obama ramps up efforts to convince the American people of the need for action in Syria, he is doing so without backing from what has been his most valued asset in nearly every other major legislative push: his grassroots army.

Organizing for Action, Obama's famed campaign apparatus turned independent advocacy group with millions of members, has been conspicuously silent in the debate over Syria. The group's aggressive social media machine, which in the past has used info-graphics, web videos and online petition drives to educate its supporters and rally the ranks, is nowhere to be found.

President Obama's personal twitter account @BarackObama, which is managed by OFA, has not once tweeted about Syria to its whopping 36 million followers. Obama himself has also refrained from direct calls on supporters to talk to their neighbors and friends and pressure lawmakers with letters, calls, emails, faxes and tweets.

Those conversations and public pressure have, in the past, been the bread and butter of Obama's strategy to winning on Capitol Hill.

The captive audience of supporters now left untapped underscores the depth of skepticism and division in the Democratic ranks about any military action. Many independent liberal groups similar to OFA, including MoveOn.org and the Progressive Campaign Change Committee, have been sounding off all week, gathering their own petitions to oppose Obama's proposal.

Today, for the first time, OFA's twitter account - with a much smaller following of 290,000 - tepidly stepped into the debate, writing, "If looking for more info as the country and Congress weigh this issue, @AmbassadorPower giving remarks now re: Syria." It included a link to the live-stream of her remarks, but OFA still does not publicly take a position on Obama's proposed strikes.

Meanwhile, Republicans claim OFA is actually undermining President Obama's efforts to build a political coalition on Syria.

Even as President Obama is trying to get GOP lawmakers on his side, his advocacy group is organizing protests of several members in their home districts. OFA is today protesting House Speaker John Boehner in Ohio for his opposition to Obamacare. Boehner, of course, has backed Obama on Syria.

UPDATE 5:15 pm ET: OFA tells ABC News it has decided not to "actively organize" on the Syria question because there is "so much going on on other issues" - a noteworthy disengagement of Obama's grassroots advocacy group at what is arguably one of the highest-stakes junctures in his presidency.

"We have heard from our supporters that they want access to more information as this debate continues in Congress," an OFA official told us. As for how the group plans to provide that information - and what type of information it might be - the official would not say on the record.

The group's executive director Jon Carson discussed the Syria issue with supporters during a regularly-scheduled conference call on Tuesday night.

"It's been pretty universal from folks that they are very glad [President Obama] is taking this issue to Congress," Carson said, according to a transcript of the call provided by OFA. "What I definitely want you all to know is that OFA supports president Obama and the agenda that Americans voted for on November 6 but we don't always actively organize around every issue and the debate in congress over the Syria vote is not one that OFA is planning on organizing around."

Carson's statement implies that supporters of the agenda that Obama campaigned on in 2012 are not united when it comes to a new war in Syria.