Senate Democrats have lost perhaps their last best chance of the year to enact meaningful opposition to the Iraq war.

A bill that would have effectively forced the Bush administration to begin drawing down the troop levels failed in its second try this year, falling four votes short of the 60 necessary to shut off debate.

That means other, stronger anti-war measures — funds cutoffs, mandatory timetables for withdrawal — are similarly doomed. Even though six Republicans have defected on the war issue, President Bush seems assured of holding onto the minimum 41 votes he needs to thwart the Democrats.

The political calculus may change under election-year pressure, but for now all the Democrats have to show for their anti-war efforts since taking control of Congress in January is Army Gen. David Petraeus’ commitment to drawing down the surge. That means by next summer matters will stand where they were in February, with 130,000 or so U.S. troops in Iraq.

This particular anti-war measure, by Sen. Jim Webb, D-Va., was thought to have the best chance of passage because it seemed troop-friendly. It would have required troops to spend as much time resting and refitting at their home bases as they spend deployed in Iraq or Afghanistan. Army units currently deploy for 15 months with 12 months between tours.

But senior military commanders complained — and in doing so changed the mind of influential Sen. John Warner, R-Va., a former chairman of the Senate Armed Services Committee — that the bill would limit the number of troops available, the point of the measure, and upset complex rotation schedules.

The measure had other drawbacks. It would have Congress too close to micromanaging the war and, further, it’s just bad policy. The best way to end the war is not cripple the military’s ability to fight it.