How long can they go this time?

Senators Rand Paul, Ted Cruz, and Mike Lee plan to hand deliver a letter to Majority Leader Harry Reid's offfice today indicating they intend to oppose moving forward on the Senate floor with " any legislation that will serve as a vehicle for any additional gun restrictions."

Politico:

Reid plans to bring up a gun-control measure that focuses on broadening background checks and cracking down on interstate gun-trafficking after the current Senate recess.

Conservatives are concerned that once that bill reaches the floor, amendments could stiffen restrictions on gun control.

Moreover, they understand that Reid intends to allow liberal amendments that would limit clip capacity and ban certain assault weapons to be offered - even though they would be defeated - to give Democrats a chance to vote on them. For moderate Democrats in competitive states, that amounts to an opportunity to vote no and show allegiance to gun rights.

Though they don't use the word "filibuster" in the letter, the conservatives are leaving no doubt that they would filibuster on an initial procedural question - the motion to proceed.

Lee staged a test vote on the issue during consideration of the Senate budget last week. He tried to amend a point of order against gun control legislation to the budget but fell short. It needed a three-fifths supermajority and failed 50-49, needing 60 votes to pass. But the final tally emboldened Lee, Paul and Cruz because they were so close to a majority and a filibuster takes just 41 votes to sustain.

With at least three conservative Senators set to go the distance in preventing gun control legislation, it seems probable that any filibuster could go on for a couple of days. And given the toxicity of the issue for vulnerable Democrats running in 2014, Reid may find himself considerably short of the 60 votes needed for cloture.

If that happens, the measure may not even see the light of day in the House and gun control would die a deserved death.