New York City Mayor Michael Bloomberg’s (I) group, Mayors Against Illegal Guns, will look to raise pressure on lawmakers to enact gun control by grading them based on their positions and votes on gun issues.

“Our coalition will not let the memory of Newtown fade," said Boston Mayor Thomas M. Menino, co-chairman of the group in a statement announcing their move.

“We demanded a plan and we got one; now we demand action from Congress,” he said. “We'll be paying close attention to the upcoming votes because the sensible reforms on the table are the very solutions that will help save lives.”

Lawmakers will be assigned a letter grade based on a scorecard that takes into account committee and floor votes, bill co-sponsorships, and public statements that will be weighted in regard to their stances on background checks; assault weapons; high-capacity magazines and gun trafficking, among other issues.

The scoring system is similar to the one already employed by the group’s primary adversary, the National Rifle Association (NRA), which gives lawmakers grades ranging from an "A" for staunch supporters of gun rights to an "F."

“For too long, the only voice that has been loud enough to influence Congress has been the Washington gun lobby’s – that’s how we’ve ended up with ineffective gun laws that have fueled our country’s gun violence epidemic,” Bloomberg said in a statement. “Now we’re working to make sure that the voices of the more than 900 bipartisan mayors in our coalition – and the 90 percent of Americans who support commonsense reforms like background checks for all gun sales – are heard loud and clear.”

The move is the latest from the Bloomberg-backed group, which has sought to rally support for gun control.

The coalition has bankrolled a $12 million ad campaign to pressure senators in swing states to back a bill that would expand background checks and increase penalties against straw purchasers.

In ads last month, the mayors’ group also aired ads featuring the parents of children killed in Newtown, Conn., urging their state legislators to pass tough new gun controls. Connecticut Gov. Dan Malloy (D) last week signed new measures into law, enacting some of the toughest gun-control laws in the country.

The group will also unveil a new ad this week featuring Neil Heslin, a Newtown father whose son was killed in the elementary school shooting, targeting specific senators.

But nationally, momentum for the Senate’s gun control bill has stalled in the face of GOP threats to filibuster any measures that they say would undermine the Second Amendment. Republicans fear that expanding background checks, which Sen. Charles SchumerCharles (Chuck) Ellis SchumerMontana's environmental lobby teams with governor to kill 600 jobs Dems allow separation of parents, children to continue, just to score political points Democrats' education agenda would jeopardize state-level success MORE (D-N.Y.) has touted as the “sweet spot” of any gun control efforts could lead to a national database of firearm owners and prevent transfers of weapons between family members.

The White House has launched a weeklong blitz to rally support, with Obama speaking in Hartford, Conn., on Monday and telling lawmakers that the victims of Newtown deserve a vote on gun control.

But Senate Minority Leader Mitch McConnellAddison (Mitch) Mitchell McConnellPolitical figures pay tribute to Charles Krauthammer Charles Krauthammer dies at the age of 68 Overnight Energy: EPA declines to write new rule for toxic spills | Senate blocks move to stop Obama water rule | EPA bought 'tactical' pants and polos MORE (R-Ky.) on Monday vowed to block any gun legislation, and demanded that Majority Leader Harry ReidHarry Mason ReidAmendments fuel resentments within Senate GOP Donald Trump is delivering on his promises and voters are noticing Danny Tarkanian wins Nevada GOP congressional primary MORE (D-Nev.) share his plans for proceeding with the bill.

It is unclear if Bloomberg’s new lawmaker ratings will hold the same influence that the NRA’s more-established ratings do.

“For decades, the NRA has done an admirable job of tracking to minute detail how members of Congress stand on gun bills,” the group’s director Mark Glaze told the Washington Post, which first reported the move. “We’ve simply decided to do the same.”

Glaze said that the scorecard was needed by donors who want more information about which lawmakers to back to help promote new gun-ownership restrictions.

“The appetite for information about where members are is very high,” he said. “We don’t intend that this will be a tree falling in the forest. We intend for people to have all the information they need to make sound voting and political-contribution decisions.”

The NRA downplayed the rival scoring system from the mayors group.

“The reason NRA scorecards are effective is that they have the weight of approximately 5 million dues-paying members and tens of millions of other supporters behind them,” NRA spokesman Andrew Arulanandam told the Post. “We’ll take that over the purse of one billionaire any day of the week and twice on Sunday.”

This story was updated at 12:41 p.m.