Seventeen members of the Senate Foreign Relations Committee took a clear position Wednesday on a resolution to approve military action against the Syrian government. Only one did not: Sen. Ed Markey (D-Mass.).

Sen. Ed Markey (D-Mass.) (Brian Snyder/Reuters)

Markey voted "present," leaving himself room to either support or oppose the measure when it comes to a vote in the full Senate. In staying on the fence, Markey did two things: 1) Invite swift criticism of his first big vote since joining the Senate in July, and 2) Expose the tough dilemma hundreds of other lawmakers are wrestling with when it comes to Syria.

Markey, a veteran of the U.S. House, won a special election for the seat once held by Secretary of State John Kerry this summer, and will face reelection in 2014. He is still finding his footing in the upper chamber, and Wednesday's vote represented his most consequential decision yet. By voting "present," Markey gave an opening to his detractors.

"He gets a check, he should vote," wrote former Republican senator Scott Brown in a Facebook post. "I did not agree with John Kerry on much, but at least he would have had the guts to vote."

The fact that Markey filled the seat vacated by Kerry — who spent hours presenting his case to the committee Tuesday — only made things look worse, said veteran Massachusetts Democratic strategist Mary Anne Marsh, who added that Bay State political observers have been "slack-jawed" in response to Markey's decision.

"I think what really sticks in the craw of people of Massachusetts is you just took John Kerry's Senate seat and you sit on the committee he chaired," Marsh said.

Markey explained his decision in a lengthy statement Wednesday. He said he needs to review more classified information and cited concerns with language in the resolution that "could be interpreted as expanding the scope of the U.S. military action beyond merely the degradation and deterrence of Assad’s chemical weapons capability." The result, Markey added, could be "deeper U.S. military involvement in a country inflamed by sectarian violence."

More broadly, Markey's decision not to take a stance is perhaps the most transparent example of how hundreds of lawmakers in both parties are grappling with the decision they face on military intervention in Syria. It's shaping up as tough call, and many have yet to take a position.

The problem for Markey is that he was one of 18 senators forced to go on the record first — and he clearly wasn’t ready to take a position.

Markey plans to continue reading hundreds of classified documents on the subject in the coming days, will continue fielding calls from administration officials and seek out the opinions of his constituents and congressional colleagues, according to aides familiar with his thinking.

Aides said Markey also believes there’s no rush to make a determination, because a final vote in the full Senate isn’t for at least another week and Obama administration officials have spent the last several days saying that a strike doesn’t need to occur immediately.

“He understands that there’s going to be a vote next week, so he’s going to take that time to make a decision,” said one aide, who asked not to be identified in order to speak frankly about the senator’s thinking.

A former Markey aide, who also spoke on the condition of anonymity to provide a candid assessment, said the senator's "present" vote is consistent with his contemplative approach to big decisions.

"I think Ed is is a very deliberative person who really likes to weigh all the facts," the former aide said. "He is very thoughtful and certainly does not take big decisions lightly."

But where some see careful consideration others will find indecisiveness.

"To me, it looks like Markey may well not have been happy with what he was presented with to vote on, but then he should have voted no and worked to change it for what he wanted it to be in the full Senate vote," said Marsh.