Sure, it's a small number of legislators, but the importance of the word "unanimous" still shouldn't be lost on you. Especially on this topic. Especially from Republicans.
And it's not being done without political backlash, as you might imagine. The National Organization for Marriage has vowed to unseat at least one of the Senators, Dennis Algiere, because of his vote.
Thanks to The Washington Post for tipping me off to this story. For more information, including links to other stories, please check out their article here.