L ike a lot of Democrats these days, Chris Murphy has been doing some soul searching. For years, the Connecticut Senator, who took office shortly after the mass shooting at Sandy Hook Elementary in Newtown, was one of the nation’s most outspoken advocates for tighter gun laws. Gun safety was so important, he argued, that supporting an assault-weapons ban should be mandatory for Democratic leaders.  Recently, Murphy has come to believe he was wrong. Not about tougher gun laws, but about trying