When a senator threatens a filibuster, the Senate holds a cloture vote to end debate on a bill, which requires 60 votes. If the cloture vote fails, the bill is pulled from the floor.

But when it comes to the latest fight over Iraq funding, Senate Dems are apparently considering a plan to force Republicans to follow through and actually filibuster.

Senate Democrats might force Republicans to wage a filibuster if the GOP wants to block the latest Iraq withdrawal bill, aides and senators said Tuesday. That could set the stage for a dramatic end-of-the-year partisan showdown, which Democrats hope will help them turn voter frustration with Congress and the stalemate over Iraq into anger with the Republican Party. Senate Majority Whip Dick Durbin (Ill.), the number two Democrat in the chamber, said a forced filibuster is “possible” and would “generate attention.”

We've heard talk like this before, but it's an encouraging sign. Stay tuned.