"As Republicans gather in Tampa to nominate Mitt Romney, Americans can expect to hear tales of how President Obama has failed to work with their party or turn the economy around," he wrote. "The truth is that the party has failed to demonstrate the kind of leadership or seriousness voters deserve."

He called Obama the "right leader for our times."

Crist could be one of several Republicans included at the Democratic convention, in an effort to prove Obama is willing to reach across the aisle. Crist, who was defeated by Marco RubioMarco Antonio RubioOvernight Defense: Tillerson, Trump deny report of rift | Tillerson says he never considered resigning | Trump expresses 'total confidence' in secretary | Rubio asks Army to kick out West Point grad Rubio asks Army to kick out West Point grad with pro-communist posts GOP establishment doubts Bannon’s primary powers MORE (R) in Florida's 2009 Senate race, has been criticized by conservatives for getting too friendly with Democrats. He switched his party affiliation to Independent in 2009.

The Democratic convention begins next Tuesday in Charlotte, N.C. The scheduled time of Crist's speech has not yet been released.