BASTARD…. As the Senate special election in Massachusetts has intensified over the last couple of weeks, voters have learned some unpleasant things about Republican Scott Brown. Yesterday’s revelation, however, is probably the ugliest.

As was first reported by Blue Mass Group, a Massachusetts-based political blog, Brown did an interview in 2008, around the time of Republican National Convention, to defend Sarah Palin as a candidate for national office. The interviewer raised the issue of the Alaska governor’s family, so the conservative state senator decided to go after Barack Obama’s parents.

“Barack’s mom had him when she was, what, 18 years old?” Brown asked, drawing a parallel between Obama’s mother and Palin’s pregnant teenage daughter. When the interviewer noted that Obama’s parents were married, Brown replied, “Well, I don’t know about that.”

The context is important here — around the time of the interview, unhinged right-wing activists were pushing the line that Obama’s parents weren’t married, a claim that became central to the bizarre Birther conspiracy theory. Brown wasn’t just attacking the future president and his parents during the interview; he was also lending credence to fringe right-wing stupidity.

For the record, there’s ample documentation to show that Obama’s parents were, in fact, married when he was born in Hawaii in 1961.

As for the Senate race, this clip has the potential to be damaging to Brown, in large part because it makes him seem like a nut. As Jon Chait noted, “By showing Brown endorsing a fringe right-wing pet theory … it’s more evidence of the fact that Brown is anything but the good government, uniter-not-a-divider moderate he pretends to be…. [O]n a visceral level, to watch him chortling as he calls Obama illegitimate is just gross and offensive. To me it exposes the man far more deeply than Coakley not knowing who Curt Schilling is.”

Much of yesterday was spent discussing Brown failing to offer health care coverage to his own staff. That’s interesting, I suppose, but defending Sarah Palin while attacking Barack Obama’s parents and endorsing a fringe right-wing conspiracy theory seems to be far more devastating in showing who Scott Brown really is.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.