Cornyn is the seventh Democrats Senator facing a primary challenge from the right . Republican must defend 21 of the 21 GOP seats up for re-election in 2014 . McConnell 's Obamacare criticism will hurt him . Strategists say earlier tea party backed challengers have hurt Senate .
Cornyn is the seventh Democrats Senator facing a primary challenge from the right . Republican must defend 21 of the 21 GOP seats up for re-election in 2014 . Strategists say earlier tea party backed challengers have hurt Senate .