Roughly five dozen Americans have died in mass shootings since the beginning of March, so naturally the details tend to blur. Nevertheless, the Pittsburgh incident stands out. On April 4, some nutcase with a private gun arsenal wigged out at his mother's house, killed three city cops, and held off a SWAT team for several hours with the help of his AK-47 assault rifle.

Yet the Democrats, traditionally so concerned about the easy availability of weaponry, said nothing.

The federal ban on assault weapons, enacted by a Democratic Congress in 1994, was allowed to expire in 2004. One might think that President Obama - who declared during the Democratic primaries that an AK-47 belongs on the battlefield, not on the street - would have cited those cop slayings as proof of the need for a new federal ban. Yet, in the aftermath of the Pittsburgh tragedy, he, too, said nothing.

Amid the ambitious sweep of the '09 policy agenda, it's easy to overlook the battles that Obama is loath to fight. Case in point: He and the Democrats are notoriously gun-shy. They don't dare clamor for a crackdown on the easy purchase of over-the-counter weaponry, because they have judged the gun-control issue to be a stone-cold political loser, now and forever. On this front in the long-running culture war, they have surrendered and the gun lobby has won.

The White House line is that any fight for the restoration of the assault-weapons ban would distract Congress at a time when the economic and health-care crises deserve top priority. That's true, as far as it goes; tangling with the National Rifle Association, and putting the squeeze on pro-NRA Democratic lawmakers, would require the expenditure of precious political capital.

But Obama's reluctance is merely the latest manifestation of Democratic skittishness, stretching back nearly a decade. The party's surrender isn't necessarily rooted in the belief that the gun-control argument lacks merit; rather, the party has made a practical determination that the issue hurts them with blue-collar white guys who view all gun curbs as akin to confiscation or privacy invasion. As a Michigan worker named Joe Overton told me during the 2000 campaign, "My brother and sister are hunters, and they think that even a photo-ID requirement is like getting tattooed."

Speaking of that 2000 race, Al Gore initially spoke out for gun control, telling CNN that "we have a flood of handguns that are too deadly." He later dumped the issue entirely, fearing that he'd lose two big gun states, Michigan and Pennsylvania. He actually won both, but he did lose Tennessee (his home state), Arkansas, and West Virginia, and to this day many Democrats say they believe he lost the presidency because Southern males dismissed him as a gun-control guy. That argument is tough to prove - Gore barely campaigned in his home state, and Bill Clinton's sex scandal alienated many cultural conservatives - but the point is, Democrats believe the gun link.

Flashing back to 1994, they also say they believe that their enactment of the '94 assault-weapons ban doomed the Democratic Congress and paved the way for Newt Gingrich's '95 GOP takeover; as Clinton later wrote in his memoir, "The NRA could rightly claim to have made Gingrich the House speaker." Actually, he overstated the case. The NRA was credited at the time with ousting roughly 12 pro-ban Democrats - but Newt's team picked up 56 seats, which means that the gun-control issue was just one of many factors, another being Clinton's health-care debacle.

Nevertheless, it's tough to dispute the recent political success of the Democrats' surrender on guns. They knew they'd never recapture Congress and the White House unless they connected with rural and working-class voters, and that meant pledging vocal fealty to the Second Amendment's right to bear arms. The strategy clicked in 2006, when the Democrats won both congressional chambers by running gun-rights candidates in culturally conservative districts and states. Then they all sat silent in 2007 when a whacked-out Virginia Tech student, taking advantage of easy legal purchase, shot and killed 33 innocent people.

Silence is the new Democratic strategy. The majority party has a big tent now. Its denizens are diverse, from coastal lefties to backwoods righties. Priority one is to protect the centrist and conservative freshmen from political harm back home; after all, there's an election next year. There's no appetite for doing anything that would put those Democrats in the crosshairs of the gun lobby.

That's why Obama's attorney general, Eric Holder, was basically told to zip his lip about any restoration of the assault-weapons ban. Three months ago, he came out for restoration; he had the wild and crazy idea that such a ban might help stanch the easy flow of assault weapons to the Mexican drug gangs who are wreaking havoc at the border. The NRA swung into action, and 65 House Democrats - many from swing districts - formally protested Holder's idea. Holder got the memo. By April, he was saying: "I respect the Second Amendment," and little more.

The polls basically show an even split between those Americans who want tighter laws on gun sales and those who don't; and an even split between those who want to ban assault weapons, and those who don't. In other words, half the nation is at least receptive to hearing renewed debate on the merits and demerits of gun control - presumably starting with the fact that, according to the Brady Center to Prevent Gun Violence, at least 41 cops have been killed or wounded by assault weapons since the '04 Republican Congress allowed the ban to expire.

But the Democrats are too cowed to even broaden the policy dialogue. It's unfortunate that, at their moment of maximum political strength, they prefer to fire blanks.