WATCH LIVE: Trump holds rally amid escalating feud with Rubio

Donald TrumpDonald TrumpMichelle Obama featured in new Clinton ad Trump camp: Dean 'went straight to the gutter' Arizona newspaper endorses Dem for president for first time MORE is capping off a dramatic day of intense attacks against Republican primary rival Marco RubioMarco RubioObama nominates ambassador to Cuba Rubio praises Marlins pitcher José Fernández on Senate floor Glenn Beck: I was wrong about Ted Cruz MORE with a rally in Oklahoma City, Oklahoma. 

Earlier Friday, the GOP front-runner was endorsed by former White House candidate Chris Christie. The New Jersey governor is expected to stump for Trump in the lead-up to next week's Super Tuesday contests.