Senate Democratic leaders late Tuesday unveiled a trio of amendments to the defense authorization bill that represent the majority’s next effort to force a turnaround in the Iraq war and isolate the White House from its Republican supporters.

“We raised the bar too high,” Reid told reporters. “They thought we could continue to send the bill back to the president — with 49 [guaranteed] votes, we couldn’t do that.”

The first amendment, crafted chiefly by Sen. Carl Levin (D-Mich.), mandates the start of a troop withdrawal from Iraq within 120 days of passage. The second amendment, crafted chiefly by Sen. Jim Webb (D-Va.), would set strong troop readiness standards and ensure a minimum period between Iraq deployments.

The third amendment, a hotly sought goal of Reid’s that was crafted chiefly by Sen. Russ Feingold (D-Wis.), would block spending on a future military presence in Iraq after April 2008, save for troops on counter-terrorism and training missions.

A possible fourth vote could come on revoking Congress’s original 2002 war authorization, a tactic favored by many but agreed upon by few. Sen. Joseph Biden (D-Del.) has suggested “de-authorization” followed by a new, targeted mission, while Sens. Hillary Rodham Clinton (D-N.Y.) and Robert Byrd (D-W.Va.) have suggested forcing President Bush to seek a new authorization from Congress.

“This is a process,” Biden said. “We’ve got to get to the point where 10 Republicans join us to get to 60, then 17 [to override a veto] … that comes from us continuing to punch, day in and day out.”

Biden said revoking the war authorization may come to a vote later in the year if not on this month’s bill. Speaker Nancy Pelosi (D-Calif.) has promised House Democrats a September vote on language similar to Biden’s.