ABC News’ Rick Klein reports: The Republican establishment is welcoming Gov. Charlie Crist, R-Fla., to the 2010 Senate race in Florida — highlighting his decision to run as a recruiting coup, and offering him an endorsement in a competitive primary. Sen. John Cornyn, the chairman of the National Republican Senatorial Committee, led a parade of Senate GOP leaders in offering immediate backing for Crist, who is seeking the Republican nomination against state House Speaker Marco Rubio, R-Fla. Cornyn, R-Texas, said in a statement: “I am pleased today to endorse Governor Charlie Crist for the United States Senate. With his record of reform in Florida, I know that Governor Crist will bring a fresh perspective to Washington in our efforts to fight for lower taxes, less government, and new job creation for all Americans.” That means the NRSC is making a choice in a competitive primary for an open seat. As Democrats are pointing out today, that’s exactly what Cornyn is refusing to do in another race that’s been in the news quite a bit of late. In Pennsylvania — where former Rep. Pat Toomey, R-Pa., is currently only major Republican candidate in the race — Cornyn had a different take on whether the GOP establishment should choose a favored candidate this far out. “I don’t think it’s wise for me to tell Pennsylvania Republicans who their nominee should be, so I’m not going to do that,” Cornyn said shortly after Sen. Arlen Specter bolted the Republican Party to become a Democrat. What makes it OK to support a primary candidate in this case? “From day one, we’ve said that the NRSC would be looking at every 2010 seat on a state-by-state basis,” NRSC spokesman Brian Walsh tells ABC. “In Pennsylvania, Senator Specter only switched parties days ago, so we’re going to see how the process unfolds out there in the months ahead, just as the Democrats are doing in Ohio where they are facing a very contentious primary. But in Florida, it’s clear that Governor Crist represents the Party’s best opportunity to keep that seat firmly in the Republican corner, and the Democrats know that as well. [Democrats] just saw one of their best pickup opportunities go up in smoke, today so you can’t blame them for doing whatever they can to distract folks from that reality.” Politically, the calculation is clear enough: Crist is a popular moderate in a critical state, running in a year where Republicans are prepared to play plenty of defense, because of GOP retirements. Republicans leaders don’t want to drain resources from the general election, and are still hoping to talk Rubio out of a run. Crist, it should be noted, has more solid conservative credentials than Specter ever did. But the decision to offer institutional support to Crist in Florida but not Toomey in Pennsylvania is unlikely to be greeted well by Toomey and his allies, including the Club for Growth. Toomey’s campaign offered no immediate comment. UPDATE (5/13/09): The conservative pushback has begun. Erick Erickson, an influential conservative blogger for RedState.org, this morning called on conservatives to boycott the NRSC because of the decision to endorse Crist. “We can disagree with the NRSC on many things, but this one is a bridge too far,” Erickson writes. And, in a shot across Crist’s bow, the Club for Growth today issued a statement saying it’s “no wonder the St. Petersburg Times reported, ‘Charlie Crist may turn out to be the closest thing to a Democratic governor Florida will see for some time.’ ” “Governor Crist still has an opportunity to reject the proposed tax hikes” in the state budget, said the group’s executive director, David Keating.