The conservatives I follow on Twitter, none more so than the boss emeritus, are tearing him and CPAC apart for this. (See Twitchy for a round-up.) But there’s an obvious explanation for why he’s invited, isn’t there?

The American Conservative Union (ACU) today announced Donald Trump will address CPAC 2013, the 40th annual Conservative Political Action Conference. America’s largest gathering of conservative leaders and activists to be held Thursday, March 14 – Saturday, March 16, 2013.

“Donald Trump is an American patriot and success story with a massive following among small government conservatives,” said ACU Chairman Al Cardenas. “I look forward to welcoming him back to the CPAC stage next week. Mr. Trump’s previous CPAC appearance was hugely popular among our attendees and we expect it will be even more popular this year.”

Philip Klein, who’s been begging CPAC to invite conservative health-care experts in order to jumpstart a serious GOP alternative to ObamaCare, wonders why they’ve resorted to “a clown show” instead:

It’s one thing to argue that there’s a strict philosophical litmus test for being invited to CPAC. Whatever one says, at least that would be a consistent position. But it’s hard to square that with the latest news that Donald Trump has been invited to speak at the gathering. For the last several years he’s emerged as one of the most prominent conspiracy theorists questioning the legitimacy of President Obama’s birth certificate and for decades, has been more concerned with creating publicity for himself and his various ventures than advancing any kind of conservative values…

What accounts for his conservative “all-star” status? How would one account for his following among small government conservatives? Is it his history of eminent domain abuse? Is it his past support for a Canadian-style socialized health care system?

The Club for Growth unloaded on him as a protectionist, tax-supporting liberal in disguise back in early 2011 when Trump first flirted with running for president. A WaPo analysis from around the same time found that 54 percent of his political donations had gone to Democrats. He used to be pro-choice and once supported big-government health care — although so did our last nominee, and not only was he momentarily a hero of the party last October, he’s invited to address CPAC this year too. (Fun irony: GOProud, which joins Chris Christie and Bob McDonnell in the persona non grata column in 2013, was responsible for inviting Trump to CPAC in 2011.) So why make an exception for the Donald, apart from the fact that he’s good copy and can deliver a crowd-pleasing red-meat Obama-bashing stemwinder perfectly well whether he believes what he’s saying or not? My guess is it’s because he’s been pounding on Karl Rove lately, a feud that dates since at least 2011 when Rove criticized him for pushing Birtherism incessantly. The fact that Rove’s building the Conservative Victory Project to try to torpedo supposedly unelectable conservative candidates in primaries has made him a sworn enemy of the grassroots, and if there’s one thing Trump’s good at politically, it’s knowing how to build conservative credibility through his choice of enemies. He got to 20 percent in the polls in early 2011 by confronting Obama relentlessly, including on his place of origin, and he’ll be a smash at CPAC if he uses his speech to rip Rove to pieces. I’m actually kind of surprised that he hasn’t gone after Chris Christie yet, as he’s arguably even a bigger villain among conservatives at the moment than Rove is. Maybe he’s reluctant to alienate a guy with a lot of sway in a region where he has business interests? We’ll see. If anyone’s next, it’s Christie.