We don’t have any inside information on who it’s from. The fact that Mitt Romney will be in New Orleans raising money for Cassidy on Oct. 3 could give an indication of it, but one questions how big a Romney endorsement of Cassidy would be.

The worn-out critique of Cassidy, after all, is that he’s an “establishment” candidate. Getting an endorsement from Romney doesn’t resolve that criticism; it reinforces it.

Sure, having Romney help you raise money is helpful. Romney is good at raising money, and while Cassidy is in better shape than anybody who’s run against Mary Landrieu money-wise, you can never have too much in your war chest.

What Cassidy really needs is a Rand Paul or Ted Cruz or Marco Rubio to drop an endorsement on him and stump a bit for him.

We’ll know shortly.

UPDATE: The National Federation of Independent Business is the endorsement. And there’s a video…