File Photo: Former Governor of Florida Jeb Bush. (Reuters)
White House hopeful Jeb Bush mustered the ultimate American put-down as he clashed with a former ally at Wednesday's Republican debate: he accused him of putting in a French work week.
Florida Senator Marco Rubio -- who like Bush hopes to steal a march on current frontrunners Donald Trump and Ben Carson -- has come under fire over perceptions he neglected his duties as he focuses on 2016.
"Literally, the Senate, is it a French work week?" Bush hit out in a fiery exchange with his Florida neighbour early in the debate in Boulder, Colorado. "Just resign and let somebody else take the job. There are a lot of people who are living paycheck to paycheck in Florida."
Many consider Rubio to be the most serious establishment challenger beyond Bush to go up against Carson or Trump, neither of whom have held elected office.
Rubio responded to Bush by saying many White House hopefuls -- including John McCain -- had missed Senate votes as they focused on the presidential race.
"Jeb, let me tell you, I don't remember you ever complaining about John McCain's vote record," said Rubio. "Someone convinced you attacking me is going to help you."
"I will continue to have tremendous admiration for Governor Bush. I'm not running against anyone on the stage. I'm running for president."
Rubio stands third in the RealClearPolitics average of opinion polls, at nine percent, well behind Trump (26.8) and Carson (22.0) but ahead of Bush (7.0).