Cornyn quotes the Buckley rule in a statement:
"I appreciate the strong support from all of my Republican colleagues, and especially our 13 new Republican Senators, as we continue our campaign to win back a Senate Republican majority in 2012. Continuity at the NRSC is something we haven’t had in a while, and which we need to build on our victories in 2010. [...]
"The key now is to build on that success, while applying lessons learned from the 2010 campaign. I believe Republicans are strongest when we stick together, and I continue to adhere to the words of William F. Buckley, who famously said: ‘I am for the most conservative candidate that can get elected.’ But I recognize that Republican primary voters choose our nominees, and I am committed to listening to the message voters sent this past year.
Of course, 2010 proved that Cornyn didn't always get it right--conservatives Pat Toomey and Marco Rubio proved to be electable, while Cornyn initially backed their opponents. And, of course, Cornyn also had a lot of recruiting successes, such as Kelly Ayotte in New Hampshire and Dan Coats in Indiana, just to name two, and posted a good fundraising year.
With unanimous support for Cornyn today and McConnell joining the anti-earmark brigades yesterday, perhaps reports of GOP disunity are overblown.