Senate Democrats on Monday lost another attempt to pass legislation forcing donors of groups that bankroll most election ads to be revealed. But Democrats, led by New York Sen. Charles Schumer, pledged to hold the Senate floor hostage and continue the debate well into the night.

The DISLCOSE Act, which was dealt the same fate in the Senate in 2010, failed to overcome a key procedural vote on entirely partisan lines, 51-44. Democrats will push for another vote as early as Tuesday after holding a “midnight vigil” to protest the GOP filibuster of the measure.