WASHINGTON (AP) &#8212 President Bush’s immigration plan to legalize as many as 12 million unlawful immigrants while fortifying the border collapsed in the Senate on Thursday, crushing both parties’ hopes of addressing the volatile issue before the 2008 elections.

The Senate vote that drove a stake through the delicate compromise was a stinging setback for Bush, who had made reshaping immigration laws a central element of his domestic agenda. It could carry heavy political consequences for Republicans and Democrats, many of whom were eager to show they could act on a complex issue that has sparked deep public concern.

“Legal immigration is one of the top concerns of the American people and Congress’ failure to act on it is a disappointment,” a grim-faced Bush said after an appearance in Newport, R.I. “A lot of us worked hard to see if we couldn’t find common ground. It didn’t work.”

Sen. Edward M. Kennedy, D-Mass., his party’s lead negotiator on the bill, called the defeat “enormously disappointing for Congress and for the country.” But, he added: “We will be back. This issue is not going away.”

Still, key lawmakers in both parties predicted that further action on the contentious issue was unlikely this year, dooming its prospects as the political strains of a crowded presidential contest get louder.

“I believe that until another election occurs, or until something happens in the body politic, that what occurred today was fairly final,” said Sen. Mel Martinez, R-Fla., the GOP chairman.

“I don’t see where the political will is there for this issue to be dealt with,” said Martinez, a crafter of the bill.

On the other side of the Capitol, House Democratic leaders signaled they had little appetite for taking up an issue that bitterly divides both parties and has tied the Senate in knots for weeks.

Rep. Zoe Lofgren, who chairs the Judiciary subcommittee that was to draft a House version of the bill, said the Senate’s “inability to move forward effectively ends comprehensive immigration reform efforts” for the next year and a half.

“The Senate voted for the status quo,” the California Democrat said in a statement.

Already Thursday, the vote had prompted a round of partisan finger-pointing. Howard Dean, the Democratic Party chairman, called it “a reminder of why the American people voted Republicans out in 2006 and why they’ll vote against them in 2008.”

The measure was the product of a liberal-to-conservative alliance led by Kennedy and Sen. Jon Kyl, R-Ariz., that forged an immigration compromise designed to withstand challenges from the left and right.

They advocated the resulting measure as an imperfect but necessary fix to the current system, in which millions of illegal immigrants use forged documents or lapsed visas to live and work in the United States. It paired the Democratic goal of legalizing those millions with the Republican desire to fortify the border and prevent undocumented workers from getting jobs.

Ultimately, though, what came to be known as their “grand bargain” commanded only lukewarm support among key constituencies in both parties, which was no match for the vehement and vocal opposition of Republican conservatives who derided it as amnesty.

“The end result was a blanket that was too small to cover everyone,” said Tamar Jacoby, an analyst at the conservative Manhattan Institute who was a strong supporter. “By its nature, because it was a compromise, it was hard to muster intense support. But the opposition was very intense.”

Conservative foes’ were among the loudest voices during the debate, led by Sens. Jeff Sessions, R-Ala., Jim DeMint, R-S.C., and David Vitter, R-La. Their views were amplified by talk radio TV hosts who repeatedly attacked the bill and urged listeners to flood Congress with calls, faxes and e-mails.

The conservatives hailed the demise of the bill as a fitting death of an effort that had thwarted the will of the American people. They faulted Bush and their own party for trying to push through a measure that lacked public support and placed Republicans in a politically tough spot.

“They made a big mistake. I think the president’s approach didn’t work,” Sessions said. Republicans “need to be careful we don’t walk into such an adverse circumstance again. This did not work out well. Our own members were placed in difficult positions.”

Bush made an unusually personal appeal for passage of the legislation, appearing at a luncheon with Senate Republicans earlier this month to urge them to put aside their skepticism. He dispatched Homeland Security Secretary Michael Chertoff and Commerce Secretary Carlos Gutierrez, as well as his top policy aides, to spend hours in Capitol Hill meetings with senators over a period of months to craft and then help push through the deal.

Advocates of the bill said lawmakers would pay a price for their inability to deal with the issue.

“Immigrant workers and families will continue to live in fear, die in the desert, and be subject to exploitation. Local communities will continue to be roiled by federal inaction and local ordinances. Voters will continue to ask why their elected leaders seem incapable of solving tough problems,” said Frank Sharry, the executive director of the National Immigration Forum, one of several liberal groups that was pushing hard for passage of the measure despite misgivings about key elements of the bill.

The bill’s Senate supporters fell 14 votes short of the 60 needed to limit debate and clear the way for final passage of the legislation. The vote was 46 to 53 in favor of limiting the debate.

Voting to allow the bill to proceed by ending debate were 33 Democrats, 12 Republicans and independent Joe Lieberman, Conn. Voting to block the bill by not limiting debate were 37 Republicans, 15 Democrats and independent Bernard Sanders, Vt. Tim Johnson, D-S.D., who has been absent from the Senate all year due to an illness, did not vote.

All of the Democratic presidential candidates in the Senate voted to end debate and advance the bill. Among the Republican candidates, only Sen. John McCain of Arizona voted to keep the measure alive. Sen. Sam Brownback, R-Kan., at first voted with McCain, but switched his vote when it was clear the bid to end debate would fail.