From today's Washington Post:
During his campaign, Obama supported reintroducing the lapsed assault weapon ban, promised to eliminate an amendment requiring the FBI to destroy records of gun buyers’ background checks and advocated closing the gun-show loophole. Since taking office, the president has done none of that, and before the midterm elections, he shelved a proposal requiring gun dealers to report bulk sales of high-powered semiautomatic rifles. In his State of the Union address, just weeks after the Giffords shooting in January, Obama made no mention of guns. ... Other leading Democrats, even those traditionally willing to offer full-throated support for gun-control efforts, have grown surprisingly less vocal as they take on more of a national role.
The Dems have lost enthusiasm for gun control. No question. But seems to me that media interest is also a big factor here. When the news media turned from Gabrielle Giffords to Libya, that's where Obama went next.
For related Cato work, go here and here.