National Republican Senatorial Committee Chairman John Cornyn (Texas) said Thursday that he has “given up” trying to persuade Florida Gov. Charlie Crist not to bolt the party and run as an Independent in the Sunshine State’s Senate race this fall.

“We’ve traded phone calls a number of times, but quite honestly I’ve given up. I thought if he wanted to talk to me, he knows how to get in touch with me,” the chairman said at a Christian Science Monitor breakfast Thursday morning. “I would say it’s been a breathtaking change of circumstances to see [Crist] contemplating taking this course after seeing his numbers plummet so dramatically.”

The comments came hours before Crist’s expected announcement that he will run as an Independent and almost one year since Cornyn warmly endorsed Crist for the Florida Senate seat.

Cornyn said he has expressed to the governor “in the strongest terms I can” that it would be a mistake for Crist to leave the Republican Party.

Cornyn said one alternative that has been proposed to Crist would be to drop out of the primary, endorse former state Speaker Marco Rubio (R) and “use the next two years to recover from his low standing in the polls” so that he could return to the political stage in 2012 to run against Sen. Bill Nelson (D-Fla.).

But Cornyn also admitted that he and the governor aren’t speaking these days.

While he’s holding out hope that Crist will change his mind before the 5 p.m. press conference the governor has scheduled Thursday in St. Petersburg, Cornyn said he’s prepared to wage a general election battle against an Independent Crist and likely Democratic nominee Rep. Kendrick Meek.

One step Cornyn said he’d take is asking Crist to return the campaign donations the chairman has made to the governor’s Senate campaign through his political action committee. He added that others who have given to Crist are already in the process of asking for their money back.

Cornyn was also in a somewhat reflective mood about his committee’s recruitment and endorsement of Crist last year.

“The funny thing about recruiting is it is a dynamic process. … It’s been a learning experience,” he said.

Cornyn said he’s learned this cycle that in the current political environment, “it’s not necessarily helpful for candidates running in states to have the national party chairman endorse them.”

Crist and the Florida Senate race were the main subjects of conversation Thursday, but Cornyn also touched on several other races across the country.

In Arkansas, where his committee is targeting Sen. Blanche Lincoln (D), Cornyn said he expects the Senator to win her high-profile primary against Lt. Gov. Bill Halter (D) but that the state continues to be “easily one of the most winnable races” this cycle. He said he believes the two leading Republicans in that crowded primary are Rep. John Boozman and state Sen. Gilbert Baker.

The chairman said he holds out hope that former Washington state Sen. Dino Rossi (R) will join an already crowded primary against Sen. Patty Murray (D).

When asked what his committee can do to persuade Rossi to throw his hat into the ring, Cornyn said, “I told him we will do whatever it takes to help him, and that’s a fact.”

And in Georgia, Cornyn said he has no concerns that Sen. Johnny Isakson’s (R) recent hospitalizations will keep him from waging a vigorous re-election campaign.

“We don’t have a plan B” in Georgia, he said. “This is not Johnny Isakson’s first rodeo.”