Collocations for challenger - noun

closest, formidable, main, nearest, serious, strong, worthy
Her nearest challenger is the vice-president.

presidential
Conservative, Democratic, Labour, Republican

face
The Senator faces a challenger with conservative views.

take on
He took on various challengers, but refused to fight Jackson.

beat, defeat

challenger for
the main challengers for the world title

challenger to
a challenger to their competitors' dominance of the market
a challenger to the prime minister