Mitt Romney's endorsement by David Keene of the American Conservative Union may be the most significant declaration of support by any individual or group on the right to date.

That's because the ACU enjoys widespread respect among most conservative activists - those most likely to vote in primaries. In addition to its annual rankings of Congress, the ACU puts on the number one conservative conference every year. The Conservative Political Action Conference draws around 4,000 attendees every year and features every conservative commentator, lawmaker, and author of note as speakers and panelists. An endorsement from Keene, therefore, carries more than a little weight.

Why Romney? Keene explained on the Laura Ingraham Show:

[F]rankly I have a lot of friends among the various candidates. I had coffee at the airport this morning with Duncan Hunter, who's been a good ? personal friend of mine for many years and continues to be a friend. I thought I'd stay out. But it's become clear in the last few months and particularly in the last few weeks that the only candidate who really has a plan that could get him the nomination other than Rudy Giuliani is Mitt Romney. Therefore, it has come down to a choice between Mitt Romney on one hand and Rudy Giuliani on the other. And I frankly don't find Rudy Giuliani all that attractive a candidate and I'm convinced that Romney has been developing the appeal that he needs to appeal across the conservative spectrum."