New York City Mayor Michael Bloomberg is ratcheting up pressure on members of Congress by starting a new system to grade them based on their votes and statements on gun issues, says the Washington Post. Mayors Against Illegal Guns, the nonprofit group financed by Bloomberg, unveils a scoring system today to award lawmakers grades of A through F, much like the National Rifle Association, which has derived much of its power by deploying letter rankings against politicians at election time. “For decades, the NRA has done an admirable job of tracking to minute detail how members of Congress stand on gun bills. We've simply decided to do the same,” said Mark Glaze, director of the group that is chaired by Bloomberg and is made up of more than 900 mayors. Glaze outlined a sophisticated algorithm that would weigh lawmakers' votes on gun bills as well as their public statements and other actions to issue overall letter grades. On the other side of the fence, Politico reports on a group called the National Association for Gun Rights in particular that is using hardball tactics against conservatives the group thinks is too conciliatory on gun issues. NAGR is airing attack ads in Virginia against House Majority Leader Eric Cantor and GOP Rep. Scott Rigell, accusing them of helping President Barack Obama create a national gun registry.