While most Senate Democrats appeared to back the bill, several liberal members said it did too little to keep immigrant families together and protect jobs for U.S.-born workers.
The split in the Republican Party was more obvious. The issue pitted social conservatives, who insisted that illegal immigrants not be granted "amnesty" for entering the country unlawfully, against business groups hungry for willing workers in hotels, restaurants, construction sites and other comparatively low-wage, low-skilled workplaces.
A bipartisan group of senators tried for weeks to bridge the chasms, but fell glaringly short Thursday night. Needing 60 votes to end debate and schedule a final vote on the bill itself, they won only 45. Senate leaders set aside the legislation until further notice.
House leaders, meanwhile, said they will not tackle immigration legislation until a Senate bill is completed.
Senate Majority Leader Harry Reid , D-Nev., said he hoped to pass the measure eventually, but he devoted much of his post-vote comments Thursday night to accusing President Bush of doing too little to obtain Republican support. "This the president's bill," Reid told a hushed chamber. "Where are the president's people helping us with these votes?"
Sen. Lindsey Graham, R-S.C., defended the administration. "The White House has worked like a dog," he told reporters. Indeed, Commerce Secretary Carlos Gutierrez and Homeland Security Secretary Michael Chertoff lobbied senators inside the Capitol right up until Thursday's showdown vote.
The White House argued the setback was not fatal for Bush's top domestic priority and urged Reid to allow the bill to continue to be debated and eventually receive a vote. Administration officials monitored the developments from Germany where the president was attending the annual summit of world leaders.
Bartlett said the president did not call any lawmakers from Germany to lobby for the measure.
Whether Bush can revive the legislation may depend largely on whether he can soften some of the differences between key components of his party's base, including the corporate community and social conservatives.
They clashed on matters such as the immigration bill's proposal for a new temporary worker program. Businesses that crave immigrant workers were furious when senators in May set the limit for incoming temporary workers at 200,000 a year instead of the original plan for 400,000. They were even more dismayed when the Senate narrowly voted to end the program altogether after five years.
But slapping tighter limits on immigration is a priority for many conservatives. When it came to the temporary worker program, their interests overlapped with those of pro-labor groups concerned about a flood of low-wage workers.
Top U.S. Chamber of Commerce lobbyist R. Bruce Josten told The Associated Press this week that the immigration issue is "divisive in the Republican base, it's divisive in the Democratic base, it's divisive in the business community. It splits organized labor, it splits the immigration community."
Republican senators who backed the immigration bill felt particularly exposed to fierce attacks from conservative activists in their home states, including talk show hosts and local GOP officials. Sen. Trent Lott, R-Miss., said in a floor speech Thursday that he disliked many aspects of the bill but felt it would be irresponsible to kill it.
"I am getting calls, but I would say to my constituents: Do you have no faith in me after 35 years that I am just going to buy a pig in a poke here, or be for something that is bad?" Lott said.
In a recent poll by the nonpartisan Pew Research Center, 55 percent of the respondents said penalizing employers who hire illegals is the best way to reduce illegal immigration . One in four said more border agents is the best answer, and 7 percent favored more border fences.
When the word "amnesty" was not invoked, 62 percent of Republicans said they favored letting illegal immigrants now in the country obtain citizenship if they have jobs, pass background checks and pay fines. But only 47 percent of Republicans said they favored giving amnesty to illegal immigrants if they met those same conditions.
Democrats, independents and moderate and liberal Republicans were most concerned about jobs, but conservative Republicans were about equally concerned with jobs and terrorism .