A new poll shows Ben Carson's net favorability rating has dropped 12 percentage points, while Marco Rubio and Ted Cruz's favorability ratings have each risen nine points. The GOP presidential candidates' favorability rankings have undergone some massive shifts, according to Gallup's Daily tracking poll. Carson has long held the largest net favorability rating among the Republican candidates, but the senators are gaining ground fast. Carson's net favorability rating is 49 percentage points, while Rubio's net favorability rating is 48 points, and Cruz's net rating is at 45 points, according to data collected from a survey conducted since November 6. "For...