They have a word for that kind of behavior: chickenshit

Wary of Donald Trump, G.O.P. Leaders Are Caught in a Standoff  (online headline).  (The New York Times, 12/1/2015)

"As Trump Barrels On, His Party is Paralyzed" (print headline).  (The New York Times, 12/1/2015)

The word is even found in respectable dictionaries nowadays.