Brett O'Donnell, right, at the Republican National Convention in St. Paul, Minn., Sept. 4, 2008. O'Donnell worked with GOP presidential candidate John McCain as his debate coach. Charles Dharapak/ASSOCIATED PRESS hide caption

itoggle caption Charles Dharapak/ASSOCIATED PRESS

Florida Sen. Marco Rubio speaks at the Ronald Reagan Presidential Library in Simi Valley, Calif. in August. Rubio's dispute with Univision has provoked a boycott of the network's presidential debate.

Jae C. Hong/AP hide caption

itoggle caption Jae C. Hong/AP