The main event in Republican presidential primary politics today: Republican candidates are trooping before an audience at the Family Research Council's values voter summit to display their conservative bona fides for one of the most discerning audiences out there on this. And some advance details of their planned speeches are beginning to leak out.

Mitt Romney appears to be poised to direct most of his firepower at the frontrunner, Rudy Giuliani. In particular, he's going to highlight Rudy's heresy on family values issues by lobbing the ultimate insult at him, comparing him to Hillary:

"We’re not going to beat Hillary Clinton by acting like Hillary Clinton."

This drew a scorching response from the Rudy camp, in a statement sent to Jonathan Martin:

"Mitt Romney's transparent pandering to anyone and everyone who will listen to him is clearly not going to end any time soon. Mitt's positions of the day and personal attacks scream of desperation from a candidate who has spent millions upon millions of his own money only to find Republican voters want something he cannot offer -- true leadership."

Meanwhile, Martin says, in his speech before the group today McCain plans to draw attention to both Rudy's current pro-choice views, and Romney's past ones, by highlighting his consistency on the issue. He'll say:

“I have been pro-life my entire public career. I believe I am the only major candidate in either party who can make that claim...You need only examine my public record to know that I won’t ever change my position to fit the politics of the day."

The main event really comes tomorrow, when Rudy goes before the group. We'll bring you that when it happens. Our guess: Rudy will blame his divorces on 9/11.