President Obama can label the failure of the Senate to approve gun control legislation "shameful." Gun reform advocates can criticize the 45 senators who blocked a bill to expand background checks as ignoring the will of the people - since opinion polls show overwhelming support for such a change.

Those who want reasonable reforms to reduce the carnage of gun violence in this nation can do all the lamenting and excuse making they want about the failure to pass any meaningful federal legislation in the wake of the horrific shooting that left 20 children dead in Newtown. But the cold, hard political calculation is this: Until enough lawmakers fear the repercussions of doing nothing about gun safety more than they fear the National Rifle Association and other gun lobby groups, no meaningful gun reform legislation will pass.

Appealing to logic is not sufficient. Requiring someone who wants to buy a gun on the Internet or at a gun show to demonstrate they have no criminal record or history of domestic violence or serious mental health issues - just as they must now pass a background check when buying from a licensed dealer - appears so obvious as to be beyond debate. Yet 45 senators lined up to say no.

Appealing to the humanity of lawmakers is not enough. Former U.S. Rep. Gabrielle Giffords, shot in the Arizona attack that left her permanently disabled and six others dead; the parents of children gunned down at Sandy Hook Elementary School; and many other gun-violence victims personally lobbied senators, asking them to show political courage. Forty-five senators disregarded their pleas.

Putting the power of the presidency behind gun safety legislation is not enough. President Obama personally lobbied senators, and made 13 speeches across the country in the fight for gun reform, but could not obtain what appeared the easiest goal - a universal background check law.

This battle now moves from a legislative struggle to a political fight. Those 45 senators - 41 Republicans and four Democrats from red-leaning states - made a political decision. They concluded the political damage they would suffer by not marching in lockstep with the NRA - the loss of financial support and the resources that could be brought against them - would be far greater than any harm resulting from disappointing gun reformists. The NRA spent $25 million in the last election cycle backing its candidates and destroying those who dare oppose their agenda.

And let's face it, Second Amendment advocates opposed to any additional restrictions on the ability to buy and own guns have been a more vocal, zealous and determined group. Until those who want reforms match that energy and sustain it, until voices and financial resources emerge that can challenge the supremacy of the NRA in the gun reform debate, nothing will change at the federal level.

But there are signs change could come. New York City Mayor Michael R. Bloomberg, serving out his last full year in office, will soon be in a position to devote more of his time, as well as his financial resources, to grow the lobbying group Mayors Against Illegal Guns. Other gun-reform advocacy groups are emerging. Families who have suffered losses due to gun violence, and who fought for reform, say they will not give up the fight.

This time, those kowtowing so completely to the NRA may have miscalculated. By spurning even the commonsense background check legislation worked out, in courageous fashion, by conservative Sens. Joe Manchin III, D-W.Va., and Patrick J. Toomey, R-Penn. - a proposal with 85 percent to 90 percent support in polls - these NRA apologists may experience a political backlash they never saw coming.

"To change Washington, you, the American people, are going to have to sustain some passion about this. And when necessary, you've got to send the right people to Washington," President Obama said after the Senate defeat.

We shall see.