On Monday the Brady Campaign to Prevent Gun Violence endorsed Barack Obama, which makes you wonder if Sarah Brady is secretly rooting for John McCain. The Brady Campaign, which maintains that the Second Amendment, properly understood, does not protect an individual right to arms, correctly perceives that Obama's avowed belief to the contrary won't prevent him from supporting its agenda. But it's hard to imagine how this kind of support can do Obama any good on Election Day, although he may be far enough ahead at this point that the qualms of the pro-gun voters the NRA is trying to mobilize against him won't make much difference.
While the NRA clearly prefers McCain to Obama, it has not endorsed the Republican nominee, for reasons that are clear from the Brady Campaign's press release. The group praises the Arizona senator for supporting gun control measures such as closing "the gun show loophole" (i.e., banning firearm transfers that don't involve licensed dealers), while criticizing him for more recently "pander[ing] to the gun lobby whose opinions he once disdained." Still, as the Brady Campaign notes, since 1994 McCain has consistently opposed the federal "assault weapon" ban, an arbitrary, ineffective piece of legislation that for Obama represents the epitome of "reasonable," "common-sense" gun control.
Correction: As a few commenters point out, after initially holding back, the NRA officially endorsed McCain last week.