HAYWORTH AND HORSES…. There’s just something about same-sex marriage that prompts conservatives to think of bizarre relations with animals. In the most infamous instance, then-Sen. Rick Santorum (R-Pa.) was asked about marriage equality, and started talking about “man-on-dog” sex.

That was seven years ago, and it’s tempting to think even Republicans would have matured a bit since. Apparently not.

Sen. John McCain’s (R-Ariz.) primary challenger, former Arizona congressman J.D. Hayworth, warned this past weekend that the same-sex marriage decision handed down by the Massachusetts Supreme Court is so loose in its logic and wording that it could lead to a man marrying his horse.

Appearing on Orlando, Fla. radio station WORL on Sunday, the Arizona conservative had what could be described as a Rick Santorum “man on dog” moment.

“You see, the Massachusetts Supreme Court, when it started this move toward same-sex marriage, actually defined marriage — now get this — it defined marriage as simply, ‘the establishment of intimacy,’” Hayworth said. “Now how dangerous is that? I mean, I don’t mean to be absurd about it, but I guess I can make the point of absurdity with an absurd point — I guess that would mean if you really had affection for your horse, I guess you could marry your horse. It’s just the wrong way to go, and the only way to protect the institution of marriage is with that federal marriage amendment that I support.”

I hesitate to bother responding to this on the merits — it’s just blisteringly dumb — but for the record, in states with marriage equality, nuptials are limited to consenting adults.

Nevertheless, it’s possible Hayworth feels the need to move way to the right on this issue because John McCain has taken a hard-right stance on gay issues. Indeed, while McCain has sometimes been labeled a moderate on gay rights, the Arizona senator, in recent years, has announced his opposition to gay marriage, opposition to civil unions (even at the state level), opposition to gays serving openly in the military, and even opposition to gay couples adopting children. This is pretty extreme, intolerant stuff.

So, apparently, Hayworth feels the need to kick things up a notch, which forces him to warn of man-horse relationships. It’s going to be quite a primary.

Steve Benen

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.