Liberal president gets equally popular at once (4,1,4)
I believe the answer is:
like a shot
'at once' is the definition.
(I've seen this before)
'liberal president gets equally popular' is the wordplay.
'liberal' becomes 'l' (abbreviation).
'president' becomes 'ike' (nickname of Dwight Eisenhower).
'gets' means one lot of letters go next to another.
'equally' becomes 'as' (synonyms).
'popular' becomes 'hot' (hot can mean popular or trendy).
'l'+'ike'+'as'+'hot'='LIKE A SHOT'
(Other definitions for like a shot that I've seen before include "Bally" , "What tequila drinkers might do" , "show partiality for spirits" , "Lout" , "to demonstrate without hesitation" .)