Buoyed by President Bush, supporters of immigration legislation established command in the Senate on Tuesday, brushing aside potentially crippling challenges to a bill that blends tougher border enforcement with a path to citizenship for millions in the United States illegally.

Members of the Congressional Hispanic Caucus, Rep. Luis Gutierrez, D-Ill., left, and Rep. Linda Sanchez, D-Calif., speak out on the Senate's immigration bill, Tuesday, May 16, 2006 during a Capitol Hill news conference. [AP]

"It was a good way to start," said Sen. Ken Salazar, D-Colo. as a shifting bipartisan coalition held firm against attacks from the left and the right.

On a vote of 55-40 that crossed party lines, the Senate rejected an appeal from Sen. Johnny Isakson, R-Ga., to require the border be secured before other immigration law changes could take place.

Anything less would mean "a wink and a nod one more time to those who would come here" unlawfully, said the Georgia Republican. The bill's supporters said he had it backward. "We have to have a comprehensive approach if we're going to gain control of the borders," said Sen. Edward M. Kennedy (news, bio, voting record), D-Mass., echoing Bush's remarks of the night before.

Hours later, Sen. Byron Dorgan (news, bio, voting record), D-N.D., made an unsuccessful effort to exclude foreigners and recent illegal immigrants from a new guest worker program that could provide jobs for millions over the next decade. "This bill is going to allow illegal workers to come in stamped as legal," he said, but the vote was 69-28 to scuttle his amendment.

Compromise averted a third showdown, when the bill's critics and supporters agreed to deny illegal immigrants any chance at citizenship if they had been convicted of three misdemeanors or a felony.

The maneuvering took place at the beginning of what Senate leaders predicted would be a lengthy debate over the most significant changes in immigration law in two decades, an election-year issue that has laid bare deep divisions inside both parties and sparked street demonstrations across the country.

The Senate bill provides additional funds for border security, the guest worker program, an eventual opportunity at citizenship for most of the 12 million illegal immigrants in the country and a tougher program of enforcement to prevent the hiring of illegal workers.

The Senate accepted two changes during the day, one by Sen. Jeff Bingaman (news, bio, voting record), D-N.M., to limit the guest worker program to 200,000 individuals a year, the other by Sen. John Kerry, D-Mass., to authorize the hiring of 1,000 additional Border Patrol agents as well as the purchase of new helicopters and boats.

Senate passage appears likely by Memorial Day.

Republicans and Democrats alike heralded Bush's Monday night Oval Office prime time speech as a turning point, at least as far as the Senate was concerned. The president announced plans to deploy as many as 6,000 National Guard troops in states along the Mexican border, and made his first unambiguous endorsement of a plan to allow millions of immigrants an eventual chance at citizenship as part of a comprehensive approach to the issue.

Sen. Mel Martinez, R-Fla., Cuban-born and a supporter of the bill, said Bush had "solidified some votes" among Republicans. He predicted that the legislation's supporters had the strength needed to defeat all killer amendments.

"The president gets it," said Sen. Dick Durbin, D-Ill., although he and other Democrats were quick to raise doubts about the commitment of numerous congressional Republicans to the approach Bush outlined.

There was ample room for doubt, as Democrats fretted that any Senate-passed bill would be changed beyond all recognition in later negotiations with House Republicans who favor a border security-only approach.

"Thinly veiled attempts to promote amnesty cannot be tolerated,' said Rep. Tom Price of Georgia, voicing the sentiment that prevails among many House Republicans. "While America is a nation of immigrants, we are also a nation of laws, and rewarding those who break our laws not only dishonors the hard work of those who came here legally but does nothing to fix our current situation."

But for now, the focus was on the Senate, where Republican and Democratic critics took to attacking the bill without success.

Isakson went first, brushing aside claims that in seeking to assure the border was under control, he was asking for the impossible. "Listen, this country put a man on the moon in nine years. This country responded to the terrorist attacks on 9-11 within three weeks. This country can do anything it sets its mind to."

Sen. John Cornyn (news, bio, voting record), R-Texas, one of the most outspoken opponents of the bill, said Isakson's proposal was designed to "put the horse in front of the cart, not the cart in front of the horse. Let's do first things first."

Democrats led the counter-attack. The party's leader, Sen. Harry Reid (news, bio, voting record) of Nevada, called it a "killer amendment." Salazar added, "In the past, for the last 20 years when we've tried to approach immigration issue by only looking at one issue at a time, we have failed." He said a "comprehensive approach was needed."

Isakson's proposal drew the opposition of 36 Democrats, 18 Republicans and one independent. There were 33 Republicans and seven Democrats in favor. The entire senior GOP leadership was among the supporters, including Majority Leader Bill Frist of Tennessee and Elizabeth Dole of North Carolina, who heads the GOP campaign committee.

"The president needs to talk to his own leaders here if he wants comprehensive immigration reform," jabbed Reid. "We've got a lot of tough votes coming up."

Frist seemed undeterred, a potential White House challenger courting conservatives for 2008, yet the leader of Senate Republican who pledges support for Bush's approach. "...Border security first, foremost. We've got to do it as part of a comprehensive plan," he told reporters. At the same time, he signaled acceptance of a portion of the bill that displeases conservatives, the part that allows some illegal immigrants to gain citizenship without leaving the country.

Eager to ward off any political danger, opponents of Isakson's proposal countered with a proposal that said none of the law's changes could take effect unless the president declared they were in the country's national interest. It passed, 79-16.

Dorgan's attack on the guest worker program went down to a defeat led by Republicans. He said the guest worker program was the price supporters had paid to win the endorsement of the U.S. Chamber of Commerce.