After shying away from the gun issue for the better part of two decades, Democratic presidential candidates now can’t say enough about the need for tougher laws, vying to see who among them can be the harshest critic of the National Rifle Assn.

It’s not that public opinion has dramatically shifted. The gun issue is the classic case in which a highly engaged minority — gun owners and their potent lobby — manage to trump the sentiments of a far-less-motivated majority. That explains why legislation requiring universal background checks for gun buyers — a proposal supported by roughly 90% of Americans — has long stalled in Congress.

Part of the shift among Democrats may be visceral, a response to the string of mass shootings that have turned place names like Sandy Hook, Aurora and now San Bernardino into grim shorthand for horrific violence.

“It’s driven by conviction,” said Paul Begala, a veteran Democratic strategist who notes that, caricatures aside, politicians are humans who bleed and cry like everyone else.

But there is also a certain political calculation.

Democrats are no longer relying on rural voters in states like Tennessee or West Virginia to win the White House. The strategy that has emerged under President Obama relies instead on a coalition of minority voters, urban dwellers and single women — groups that look far more favorably on gun controls — in battlegrounds such as Virginia, Colorado and Nevada.

It’s not that Democrats have grown any more ardent in their support of tougher gun laws, it’s that “Democrats are freer now to talk about gun control because they feel it’s not going to cost them votes on election day,” said Adam Winkler, a UCLA law professor and author of “Gun Fight: The Battle Over the Right to Bear Arms in America.”

That said, Winkler suggested that regardless of how strongly a Democratic president supports gun control, no new restrictions are likely to pass into federal law so long as control of Congress and the executive branch remain divided between the parties.