Mitt Romney calls Barack Obama `` the worst president this country has ever seen '' four of the four Republican presidential candidates campaign Tuesday . CNN 's Jim Acosta , Rachel Streitfeld , Tom Cohen and Adam Aigner-Treworgy contributed to this report . They take jabs at Obama ahead of the State of the Union address . Mitt Romney releases his Tuesday tax return .
Mitt Romney calls Barack Obama `` the worst president this country has ever seen '' four of the four Republican presidential candidates campaign Tuesday . They take jabs at Obama ahead of the State of the Union address . Mitt Romney releases his Tuesday tax return .