After the Virginia Tech shootings in 2007, when 32 people were slaughtered by a mentally disturbed young man wielding two semi-automatic pistols, calls for enhanced gun control were met with a warning from Democratic Senate Majority Leader Harry Reid. Sen. Reid cautioned against a “rush to judgment” about new gun laws.

But after the Arizona shooting of last week, gun control measures are being discussed again, and Mr. Reid hasn’t said anything cautious.

Why the change?

The National Rifle Association was one of the big losers of the 2010 midterm elections.

This is so, even though 85 percent of its endorsed candidates won, and the percentage of gun-loving Senators and House members rose after the election.

The difference is that the NRA can no longer claim to be anything but an appendage of the Republican Party.

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One of the key components of the NRA’s power has been the support of moderate and conservative Democrats. Even when the Democrats controlled Congress, there were more than enough pro-gun Democrats to vote with most Republicans and bat down any efforts at gun control.

NRA's historic reach with Democrats gone

Think back to March 2009, when a newly installed Obama administration, with strong majorities in the House and Senate might have contemplated reinstating the assault weapons ban. (The ban was implemented in 1994 under the Clinton administration, and the Bush administration let it expire in 2004). The NRA cracked the whip, and 65 House Democrats signed a letter declaring eternal opposition to such legislation.

Just two years later, only 26 of the signers of that letter are still in the House. Many got creamed this November, despite NRA support.

Of 50 key NRA-endorsed incumbent House Democrats, only 23 survived the midterms. Not only did most NRA Democrats lose, but NRA-endorsed losers made up half of all defeated House Democrats.

The NRA’s endorsement is about as useful to a Democrat as a duck decoy to a deer hunter.

What can the NRA do for any Democrat when it counts, on Election Day?

In the past, (now defeated) Democrats like Stephanie Herseth Sandlin of South Dakota or Brad Ellsworth of Indiana could use NRA endorsements to win over those single-issue independent voters whose mantra was “guns über alles” (guns above everything else).

Today, such voters are mostly committed Republicans. They won’t vote for a Sandlin or an Ellsworth just because of an NRA endorsement.

The price of partisan support

And if they can’t get any votes by stopping gun laws, then Democrats have to consider how many votes might be gained by supporting sane, popular gun-control legislation such as limits on assault weapons, closing the gun show sale loophole, and the administration’s plan to force gun stores to report multiple long-gun sales, just as they do with handguns.

Why, Democrats might even support legislation to make it as hard for terrorists to buy guns as it is for them to board planes! Or go back to the law we had from 1994 to 2004 that limited the size of magazines sold. The Arizona shooter was stopped as he reloaded; with a magazine only half the size, many now wounded or dead might have escaped unhurt.

The Democrats have been unable to unite behind any of these bills for years for one simple reason. Many of their leaders believed that gun control cost the party the 2000 presidential election, since pro-gun voters in Tennessee turned on favorite son Al Gore to punish him for the Clinton assault weapons ban.

However true that was then, the lesson of 2010 for Democrats was that the NRA doesn’t deliver for Democrats anymore.

Don't expect much gun-control legislation anytime soon. Historically, it takes at least a few years after a massacre or assassination to get sensible laws passed. Certainly, there’ll be no progress on gun control while the House is in Republican hands.

But the next time the Democrats have both houses of Congress and the White House, expect real gun control to move for the first time in years.

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When an interest group’s supporters only rally to politicians of one political party, that interest group’s fortunes rise and fall with that party.

Just ask the AFL-CIO.

Jeremy D. Mayer is an associate professor in the School of Public Policy at George Mason University.