Asked if he had been contacted by the White House in an attempt to change his vote, Begich said, laughing: "Let me just say, I don't think the White House is very happy with me today."
Sens. Kay Hagan of North Carolina, Mary Landrieu of Louisiana, Mark Pryor of Arkansas, and Jeanne Shaheen of New Hampshire, who are also facing strong opposition for reelection, all voted in favor of the package.
But not before they cast votes in a rebuke of the president, joining Republicans in favor of a procedural vote that Sens. Jeff Sessions of Alabama and Ted Cruz of Texas called for as an implicit vote to halt the administration from taking executive action to aid child immigrants later this year. The amendment failed to clear the 51 votes it needed to carry.
As for the Republicans facing difficult 2014 campaigns, Sen. Pat Roberts of Kansas voted against the continuing resolution and Syria authorization package, while Senate Minority Leader Mitch McConnell voted with the majority in favor of the bill.
The CR, which was necessary because Congress failed to agree on any appropriations measures for fiscal 2015, keeps government running at its current $1.012 trillion annual funding level through Dec. 11. The legislation also sunsets the military authorization on the same date.
That legislation allows the White House to train rebels, who officials say will be "vetted," and amounts to a win for the administration, which dispatched Secretary of State John Kerry and Joint Chiefs of Staff Chairman Martin Dempsey to convince lawmakers that they should back the president's plan.
The administration may be getting what it wants for now, but it will have to persuade lawmakers again in December. Training the rebels could take up to eight months, Dempsey told senators this week. So it seems certain the president would need Congress's help again.
Whether he gets that support is uncertain, and there are other wrinkles.
Key Senate Democrats support a broader authorization for the use of military force, but so far it's unclear if the White House wants the same thing. Obama has said he would engage Congress on this issue and wants to repeal the 12-year-old AUMF in May 2013.
Assistant Majority Leader Dick Durbin of Illinois, a key Obama ally in the Senate, said the chamber will take up the issue.
"Beyond this vote—which is not the authorization of using military force by the United States—beyond this, we're going to take up the construction of a new authorization for the use of military force," Durbin said. "It's long overdue."
Armed Services Committee Chairman Carl Levin of Michigan, who's retiring at the end of the year, suggested this week that another authorization could be added to the defense authorization bill, which Congress must take up when it returns in November. Or, Levin said, lawmakers could pass a new authorization for the use of military force to replace the now 12-year-old measure passed under the George W. Bush administration and aimed at Iraq. Senate Foreign Relations Committee chairman Bob Menendez, D-N.J., said last week that his panel would begin composing such an authorization.