/shrug
Political theatre. It's totally based on the idea that God hasn't revealed Godself.
It's easy to take 2 cases:
Case 1: God doesn't exist; this agnostic senator is calling attention to the lack of evidence that supports this case. Nobody can prove it's true or false, and eventually people get bored and hopefully go back to doing something productive in Washington.
Case 2: God does exist; this agnostic senator's lawsuit calls attention to the lack of evidence for God. Nobody can prove it's true or false, and eventually people get bored and hopefully go back to doing something productive in Washington.
For the record, I voted "No" on the poll, but really, who cares? I don't think anyone expects God to appear as a white-robed, bearded, old caucasian man, prove "his" identity through various pyrotechnics until even the most skeptical atheist admits that it couldn't possibly be staged, and then sit calmly down with the senator in a court of law and explain why "he" hasn't snapped his fingers for a perfect world (Matrix 2, incidentally, gave a crap 30-second version of the ancient "best-possible-world" thesis).
So yeah, /shrug at political theatre, and I sort of wonder if that senator's district feels like he's wasting the time he's supposedly using to represent them. Separation of church and state, you know? I don't really care whether the senators believe some God exists, but if they're spending their political day drafting up cutesy legal briefs to foreground the fact that God doesn't live in the US of A . . . well, next election cycle I'll try to find someone with some ambition.