Conceding that the sharply limited gun control legislation before the Senate won't stop every gun murder, Mark Kelly, husband of former Arizona Rep. Gabby Giffords shot in the head in 2011, claimed that it will help to quell gun violence in the nation.

"This bill," he said, "will not stop every murder from a gun."

Kelly, who this week is personally lobbying senators to support the effort to expand background checks on gun owners, is comparing the legislation to the decades old Clean Air Act in how it helped to reduce pollution.

"The Clean Air Act in the 1970s did not get rid of all pollution. But it got rid of a lot of it and it made our air cleaner and our lives a lot healthier and we can do the same thing with gun violence if we enact some reasonable legislation," he told reporters at a Christian Science Monitor briefing Tuesday.

Amid reports that the background check compromise crafted by Democratic Sen. Joe Manchin of West Virginia and Republican Pat Toomey of Pennsylvania is unlikely to pass, Kelly said he was frustrated with Washington and especially the National Rifle Association which has threatened to give "F"s to lawmakers who vote for the legislation. As a result, he added, "there are a lot of senators just looking for a reason to get to 'no.'"

To counter that, the group Kelly and his wife created to push gun control, Americans for Responsible Solutions, will try to counter the NRA by supporting House and Senate challengers to those who oppose gun limits. "We will be there to try and replace them," Kelly said.

But being tiny by comparison to the NRA, he conceded that it will take a few elections to build the influence and power to win. But he already has a target: Family friend Sen. Jeff Flake, the Arizona Republican who said he will fight the Manchin-Toomey compromise.