For the first time in more than a decade, Democratic presidential aspirants see a political advantage in championing far-reaching restrictions on guns.

In Massachusetts on Thursday, Gov. Deval L. Patrick (D) unveiled a sweeping set of proposed restrictions that would restrict access to high-powered ammunition, broaden background checks and restrict gun purchases to one per month.

Earlier in the week, New York Gov. Andrew M. Cuomo signed into law the country’s toughest assault weapons ban and limits on ammunition magazines, saying that “no one needs 10 bullets to kill a deer.” Maryland Gov. Martin O’Malley and Colorado Gov. John Hickenlooper are also pushing gun reforms in their states.

And in Washington, Vice President Biden led formulation of the Obama administration’s plan to curb gun violence announced this week. Speaking to the U.S. Conference of Mayors on Thursday, Biden said the Dec. 14 massacre of 20 children and six adults at a Newtown, Conn., elementary school had changed the political dynamics of gun control.

“There are some who say the most powerful voice in this debate belongs to the gun lobbies and those that demand the stop to these common-sense approaches to save lives,” Biden said. “I think they’re wrong. This time — this time will not be like times that have come before. Newtown has shocked the nation. The carnage on our streets is no longer able to be ignored.”

How the NRA exerts influence over Congress

The moves by the five men — all potential presidential candidates — mirror a broader shift among Democrats, who have generally shied away from pushing any significant gun-control legislation since Al Gore’s defeat in a 2000 campaign that included a fiery debate over weapons restrictions.

“Finally, Democrats are getting out of Plato’s cave when it comes to guns and are not fearful of their own shadow on this issue,” strategist Chris Lehane said. “Democrats used to play defense. Now you have Democrats who recognize this is a winning issue and are playing offense on the issue.”

On the Republican side, some of the potential contenders for 2016 are lying low on the issue, leaving it primarily to the National Rifle Association and conservative lawmakers without national ambitions to make arguments against further gun regulations. One exception is Sen. Marco Rubio (R-Fla.), who blasted Obama’s gun-safety proposals as an infringement on Second Amendment rights.

The Democratic shift is remarkable given more than a decade of near silence on gun issues within the party. During the 2000 Democratic presidential primaries, challenger Bill Bradley lured Gore into a debate over gun laws — then, as now, a hot-button culture-war issue.

“I’m not sure that it was our preference to run on guns, but it was a necessity to take a tough stand on that issue,” said Robert Shrum, one of Gore’s top strategists. “You had to. It was a litmus test in the Democratic primary.”

After Gore narrowly lost the White House, Democrats widely concluded that it was best to stay away from guns on the national level.

In 2008, the issue was so absent that Republican operatives struggled to find any video evidence of then-Sen. Barack Obama’s support for an assault weapons ban. Their best hit? An audio recording of Obama telling donors that white working-class voters sometimes “get bitter and they cling to guns or religion.”

Now, however, the guns debate is becoming a litmus-test moment for Democrats who hope to succeed Obama in the White House. “In the primaries in 2016, you’ll have people look back to see where candidates were in the first part of 2013,” Lehane said.

Among Republicans, some potential candidates apparently feel pressure to offer solutions. Louisiana Gov. Bobby Jindal (R) announced a plan last week for his state to share data with the national criminal background check system designed to keep firearms out of the hands of the mentally ill.

And New Jersey Gov. Chris Christie (R), while dodging a question about whether he supports an assault weapons ban, said last week: “The fact is, I’m willing to have that conversation. That’s more than a lot of people will say.”

On the Democratic side, Secretary of State Hillary Rodham Clinton — who would instantly become the front-runner if she decided to run — fell ill shortly after the Newtown shooting and just returned to work last week. But her husband, former president Bill Clinton, took a strong stance against high-capacity ammunition clips in a recent speech.

Sen. Kirsten Gillibrand (D-N.Y.), considered a potential national candidate, is among those leading the charge in the Senate for stricter gun laws. Cuomo, meanwhile, was dubbed “America’s Sheriff” by the Daily News after calling for prohibitions on the sale of military-style assault weapons and ammunition clips over seven bullets.

In Maryland, O’Malley, a former Baltimore mayor who used his record of fighting crime to propel him to the governorship, is pushing to ban assault weapons and high-capacity magazines, require new licensing rules, strengthen school security and aid those with mental illness.

O’Malley unveiled the proposals at a gun-policy summit Monday in Baltimore headlined by New York Mayor Michael Bloomberg (I), a leading gun-control advocate. “There is a sickness in our country, and that sickness is gun violence,” O’Malley said.

But the biggest platform is occupied by Biden, who is said to be eyeing a third presidential run in 2016. Biden has taken center stage during the past month as he met with interest groups while fashioning the administration’s gun plans.

Biden wrote a now-expired assault weapons ban as a U.S. senator in 1994. In his speech Thursday, he sought to play down his influence on Obama’s package of gun-control measures, which include a new assault weapons ban, limits on high-capacity magazines and universal background checks for firearms purchasers.

“I’ve been getting both credit and blame for that, as if these were original ideas of mine,” Biden said. “I want to make it clear what every deputy mayor knows: The only power or influence a vice president has is reflected power. None of it matters, no matter what someone tries to give you credit for leadership, if it were not for the leadership of the president of the United States.”

But Shrum said that Obama’s proposed assault weapons ban will improve Biden’s standing within the Democratic Party, regardless of whether Congress passes it.

“If Obama can get something done, it will be to his credit and to Biden’s,” Shrum said. “And then if Biden runs, he’ll say, ‘I wanted to do more, and as president I will do more.’ I don’t see that that issue can cut against Biden.”

Felicia Sonmez contributed to this report.