Without the crucial support of Sen. John Warner (R-Va.), Senate Democrats failed for the second time to pass a bipartisan proposal to give war-weary troops mandated time at home Wednesday — a striking defeat that made further bipartisan deals on troop withdrawals from the Iraq War even more remote.

Democrats effectively had a net loss of one vote in the 56-44 tally and did not pick up any new Republican support. Sixty votes were needed to pass the measure.

Though a handful of GOP Senators had expressed a potential willingness to support Sen. Jim Webb’s (D-Va.) proposal, Warner’s decision to change his vote meant that only six Republicans voted to give soldiers time at home equal to their deployments in war zones — a response supporters said would address the fact that many soldiers have been forced to endure unusual 15-month tours with little time off between deployments to war zones in Iraq or Afghanistan.

Warner’s decision “caused a number of other Republican Senators to not come our way,” Webb said.

A similar amendment also got 56 votes in July with the support of Warner and the other six Republicans. But at that time, Sen. Tim Johnson (D-S.D.), who supported the amendment, was recovering from a brain aneurysm. Johnson voted for it Wednesday.

By a vote of 55-45, the Senate also rejected a nonbinding amendment stating that soldiers should be “afforded as much ‘dwell time’ as possible in their home stations prior to redeployment” and that the Pentagon should endeavor to establish an equal-time troop rotation policy. The proposal also faced a 60-vote hurdle to passage.

Though rumors abounded earlier this week about Warner’s potential switch, the retiring defense hawk, who is widely respected in both parties, announced his decision on the Senate floor after coming under intense pressure from Defense Secretary Robert Gates and top Pentagon officers.

“When it became possible, if not likely, that we were going to get 60 votes, the White House really revved up the engines,” Webb said. Gates, in particular, “turned up the heat and I think that made people like Sen. Warner, particularly, very uncomfortable,” Webb added.

Senate Majority Leader Harry Reid (D-Nev.) said Democrats were “surprised and terribly disappointed” by Warner’s change of heart. Warner’s new doubts and his invitation for two three-star generals to brief four wavering Republicans on Wednesday afternoon undoubtedly affected the outcome of the debate.

None of the four who attended the Warner-Pentagon briefing — Sens. Lisa Murkowski (Alaska), Lamar Alexander (Tenn.), Bob Corker (Tenn.) and Arlen Specter (Pa.) — voted for the amendment.

In a rambling 23-minute floor speech, Warner gave several reasons for his turnabout, not the least of which was the president’s decision to follow his advice — and that of his commanders in Iraq — to bring 5,000 troops home before Christmas. The president announced last week that 5,700 soldiers would return by then.

“That put me in a different posture because I felt that my thought: ‘It’s time to bring some people home,’ was accepted and therefore, my thoughts then turned to the Webb amendment and the need to go back and get a clear understanding from the United States military … of the consequences of the well-intentioned principles of the Webb amendment,” Warner said.

Warner said Gates and Pentagon officials told him the amendment would create a force management crisis and that they could not possibly implement the troop rotation cycle envisioned by Webb within the 120 days the amendment would have provided.

Though Warner said generals told him they might be able to manage the change if given until October 2008, he noted that Gates was unwilling to negotiate on alterations to the amendment.

“I did my very best, but that was not achievable,” Warner said.

Warner, who spent the bulk of Monday traveling in Virginia with Gates, also cited a threatened presidential veto as a causing his switch.

“I just don’t want to see another veto scenario here right in the middle of a war. That’s another reason,” he said.

Corker said he talked with Webb a few weeks ago and had “been open” to the amendment. But after leaving the Warner-Pentagon briefing, Corker said he would not vote for the proposal.

“While the goal of the amendment is very good … it’s just not practical,” he said.

Corker said one of the generals’ key arguments was that the rotational cycles mandated by the amendment would force them to call up even more National Guard and Reserve units, which military experts have said already are overused.

Before voting, Specter asked Webb to modify the amendment so that it would not take effect until October 2008 and complained that Senators needed more time to evaluate it.

“I think that if there was an understanding by other Senators about the ability of the Department of Defense to meet a 2008, Oct. 1, date … that there might be some additional interest,” Specter said on the floor. He added later, “In the course of the remaining time before the roll is called, I’m going to see if it’s possible to find some constructive way forward and some rational basis for the vote that I will cast.”

Republicans said the Pentagon lobbying effort against the amendment was the primary reason it failed. Specter, for example, detailed four contacts he had with generals, Gates and National Security Adviser Stephen Hadley in the past week.

“The Pentagon hadn’t before given us a lot of specifics of what it would mean,” said one Senate GOP leadership aide, adding that that had made it more difficult for GOP leaders to dampen centrist defections in July.

Meanwhile, Senate Democrats will continue to push for a more accelerated drawdown of troops in Iraq as part of the larger debate on the Defense Department authorization bill, even as their prospects for a filibuster-proof majority dim.

Senate Armed Services Chairman Carl Levin (D-Mich.) said the Senate likely will hold a vote on his proposal to force an end to combat missions in Iraq and transition to a limited mission of counterterrorism, training of Iraqi forces and protecting U.S. assets within nine months of enactment.

If that fails to attract 60 votes, as appears likely, Levin reiterated his intent to offer a similar amendment that would simply set a goal for completion of the transition, the timeline for which may or may not be nine months.

Despite the appearance that both parties have dug into their positions following last week’s testimony by U.S. commander in Iraq Gen. David Petraeus, there were still calls for bipartisanship.

“I think it would be a very helpful thing if the Congress and the president could come to agreement on a policy and a plan without leaving it solely to the discretion of the executive branch,” Specter said.

But President Bush was having none of it Wednesday. Asked whether he might support Congressional legislation to implement the recommendations of the bipartisan Iraq Study Group, Bush said, “My attitude is, I accept what Gen. Petraeus recommended, not what [Members of Congress] recommend.”