Democratic Senate hopeful Justin Wagner late yesterday posted a web-only video that hits Republican incumbent Sen. Greg Ball for voting against the successful effort to legalize same-sex marriage, one of the first instances in which a GOP incumbent in New York is knocked for his 2011 vote.

The video uses Gov. Andrew Cuomo’s speech following the nail-bitter of vote in the state Senate in which he says the measure was about equality and fairness. The Wagner campaign splices video of Ball in a subsequent interview saying “That’s why I voted against it.”

It’s potentially effective, though Ball’s campaign would certainly take issue with the premise.

Ball says didn’t vote against the law because of fairness, but because of his concerns over religious protections. Ball was one of several Republican lawmakers who were publicly on the fence over the issue, which garnered him a lot of press, but he ultimately voted no.

Still, the video from Wagner is something of an outlier among his Democratic colleagues.

Senate Democratic candidates have largley not used the same-sex marriage issue in the campaign (nor has any Democrat really mentioned Republican Sen. David Storobin’s bill to repeal the law).

Part of the reason is because the Senate Republican leadership allowed a vote for the bill in the first place, a move that blunted what would have been an expensive campaign from the LGBT community and its wealthy class of donors who would view a Democratic takeover of the chamber the only course for legalizing same-sex marriage.

That is not the universe we live in, however.

Senate Democrats do not enjoy the cash infusion for pro-gay marriage candidates this year. Meanwhile, Sen. Joe Addabbo, a Democrat who actually switched his 2009 vote from no to yes, is facing a stiff challenge from Queens Councilman Eric Ulrich.

Meanwhile, Republicans who voted for the measure were showered with generous donations from a variety of advocates. The unanswered question remains: Why no support for Addabbo?