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While President Obama was in St. Petersburg, Russia, on Thursday, trying to sway skittish allies to back a military strike on Syria, thousands of miles away in St. Petersburg, Fla., residents were leaving little doubt that Obama has a lot of work to do if he's to gain their support for military action.

Lawmakers in and around the coastal city say their constituents are almost uniformly opposed, or at least cautious, on a strike. Rep. Kathy Castor, D-Fla., who represents the city, wrote to Obama saying her neighbors are "extremely wary of military action."

Republican Rep. Rich Nugent, who represents a nearby district, told FoxNews.com his office has gotten 1,800 calls and emails opposing action in Syria, and only 17 in favor.

"You usually don't see any kind of split like that," Nugent said. The overriding concern, he said, is that America could get drawn deeper into the fight.

The lawmakers are not alone. House members across the country are fielding thousands of calls and emails from constituents telling them to oppose the Obama administration's push for a military strike. Though Obama is winning on one front -- he's gotten the endorsement of congressional leaders, and of a key Senate panel -- he's clearly losing when it comes to the battle for public opinion.

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    Polls show that any military strike, even a limited one, remains deeply unpopular. And those opposed to a strike are making their views known, complicating passage of a use-of-force measure.

    The backlash adds pressure to the president to, when he returns from his visit to Russia where he's attending the G20 summit, directly address the American people to make his case. (In his absence, the White House on Thursday launched a website dedicated to making the case for a Syria strike.)

    Nugent, in a letter to Obama, urged the president to "articulate the threat to our national security, to articulate your plan for eliminating that threat, and to seek the people's approval for your action." Nugent, though, argues that for him, the "moral argument" for a strike is simply not enough to justify it.

    Democratic strategist Mary Anne Marsh, who supports a strike, said the president may very well have to play the role of "closer" in order to sell this to the American people.

    Marsh, who used to work for former Sen. John Kerry before he was secretary of State, said the bar for any military action is "very, very high" these days in the wake of the Iraq war. She told FoxNews.com the administration has to do a better job of explaining the rationale for a strike, and specifically explaining why the U.S. has an interest in punishing Assad for using chemical weapons.

    Making that case herself, she said: "Chemical weapons (are) in a special category that belongs in hell by itself."

    At the moment, many lawmakers and their constituents don't see the urgency.

    "I have spoken to hundreds of constituents," a fired-up Rep. Jeff Duncan, R-S.C., said during a House committee hearing on Wednesday. "Not a one ... in my district in South Carolina or the emails of people that have contacted my office say, 'Go to Syria and fight this regime.'  To a letter they say, 'No, do not go into Syria.  Don't get involved in their civil war.'"

    Kerry and other top administration officials who testified on the Hill this week argued persistently this would not be a "war" in the classic sense. They, like the president, describe it as a "limited" military action meant to punish the Assad regime for using chemical weapons and deter other regimes from doing the same.

    But that hasn't stopped lawmakers from throwing the "w" word around, with skeptics raising the specter of everything from Iraq to Vietnam.

    "Vietnam started with U.S. advisers in a limited naval presence. It led to an all-out war and a quagmire that cost lives of thousands upon thousands of U.S. servicemembers," Sen. Tom Udall, D-N.M., warned on Wednesday, as the Senate Foreign Relations Committee on which he sits voted to advance a Syria strike resolution.

    The full Senate could take up the measure as early as next week. But the bigger problem for Obama may be the House, where members face re-election next year and are hearing from angry constituents by the hundreds.

    U.S. representatives on both sides of the aisle took to Twitter this week to talk about the pulse of the nation on the Syria question.

    "FYI: Not 1 (one) constituent has told me they are in favor of action in Syria. As of this second. In other words: 100% opposed," Rep. Tim Griffin, R-Ark., tweeted.

    "So far about 500 emails regarding Syria. 499 say NO and 1 says YES go to war," Rep. Jason Chaffetz, R-Utah, tweeted on Wednesday.

    And on Thursday, liberal Democratic Florida Rep. Alan Grayson said "people here listen to their constituents -- public opinion is vehemently against it."

    Obama has been able to move the needle of American opinion since making his case that the Syrian government used chemical weapons to deadly effect on Aug. 21. But the needle has moved only slightly.

    A Pew Research Center poll released earlier this week showed people still are opposed to military strikes in Syria 48-29 percent. The president faces the deepest opposition among members of his own party.

    People are concerned about the possibility that limited strikes could escalate, and that the airstrikes might not be effective. It is no coincidence that these were the concerns voiced by lawmakers during hearings on Capitol Hill.

    On the House side, lawmakers appear to be waiting for the Senate to act before moving on a resolution of their own. But virtually no one believes the votes are lined up in the House right now to pass a use-of-force measure. Though the Republican and Democratic leaders of the House endorsed the president's push, informal whip counts show a daunting picture for the administration.

    The liberal blog ThinkProgress estimated that just 48 members of the House have said they'll back the resolution.

    But on the Senate side, the most ardent supporters of military action are making their case, to the American people and fellow lawmakers.

    Sen. John McCain, R-Ariz., who temporarily opposed the use-of-force measure before winning additional concessions and voting for it on Wednesday, told Fox News that the main concern among voters is the possibility that ground troops could go into Syria. The administration says that would not happen.

    "Americans don't want boots on the ground," McCain said. "They have to be assured of that, and they have to be confident of that if they're going to support this measure."

    Fox News' Nick Kalman contributed to this report.