SENATE TO TAKE UP THUNE AMENDMENT…. Yesterday, the Senate took up an amendment on F-22s as part of the military’s budget bill. Today, lawmakers will likely consider another amendment, which is even more controversial.

Nearly all states issue licenses to carry concealed firearms, but the criteria for granting such permits vary widely, and it is now, sensibly, up to each state to decide whether to accept another state’s permits.

At least 35 states prevent people from carrying concealed weapons if they have certain misdemeanor convictions. At least 31 states prohibit alcohol abusers from obtaining a concealed carry permit and require gun safety training. The Thune amendment would force states with more restrictive standards to accept concealed carry permits from states with less stringent rules — in effect giving the lax rules national reach.

Passage of the amendment would make it much harder for law enforcement to distinguish between legal and illegal possession of a firearm. It would be a boon for illegal gun traffickers, making it easier to transport weapons across state lines without being caught.

Thune has the enthusiastic backing of the NRA, while some Senate Democrats, hoping to derail the measure with a filibuster, have the support of more than 400 mayors, who took out an ad in yesterday’s USA Today to denounce the Thune amendment.

Opponents are being led in large part by Sens. Chuck Schumer (D-N.Y.) and Frank Lautenberg (D-N.J.), but whether they can get 41 votes together remains to be seen. Despite the large Democratic majority, three Senate Democrats – Max Baucus and Jon Tester of Montana and Mark Begich of Alaska – are co-sponsors of the measure, and Sens. Harry Reid (D) of Nevada and Ben Nelson (D) of Nebraska both announced their support for the amendment yesterday.

The administration hasn’t had much to say about this, suggesting that if the larger spending bill passes with Thune’s amendment in the legislation, it will become law.

Postscript: In case anyone’s wondering, I think the Thune Amendment is a bad idea, but I’d still rather get rid of the filibuster. If a bad idea enjoys the support of a Senate majority, it should pass. If people with good ideas want to try to undo it at some point in the future, they should do their due diligence. And if they come up short, we’ll have the laws we deserve, as passed by our elected representatives.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.