He is talking about how Senators are lonely, and desperate for love, or something.
You know, all three of us spend a lot of time covering politicians and I don't know about you guys, but in my view, they're all emotional freaks of one sort or another. They're guaranteed to invade your personal space, touch you. I sat next to a Republican senator once at dinner and he had his hand on my inner thigh the whole time. I was like, ehh, get me out of here.
And some people are like, "who is he talking about? Lindsey Graham? Mitch McConnell?" And other people are like he is such a sexist because he is freaked out by sexual harassment and that happens to ladies all the time and he doesn't care!
But, yeah, it really just seems like a really lame attempt at a gay panic joke of the sort that old straight dudes always think are funny. "One of those queers touched me once, it was gross!" And the fact that "Republican senator" can basically stand in for "one of those queers," in that joke, as made by a conservative columnist, is proof of how far we have come, as a nation.