In an election, those in power should feel obliged to compete ______ their…

“Compete” takes different prepositions depending on what follows it: “compete with/against” a rival, “compete for” a prize, “compete in” a contest. When it is paired with the fixed expression “on equal terms” (meaning neither side has any built-in advantage), standard English idiom locks onto one specific preposition rather than the other general rivalry-preposition.

In this sentence, the blank sits between “compete” and “their opponents”, and is immediately followed by “on equal terms”. Because the sentence needs the exact collocation “compete with somebody on equal terms” — the standard way of saying a contest carries no built-in advantage to either side — the word “with” is what completes it correctly.

• “towards” expresses the direction of a feeling or attitude (e.g., an obligation towards someone), not a competitive relationship, so it cannot follow “compete”.

• “against” can generally follow “compete” to name a rival, but it does not combine with the fixed phrase that follows the blank in this sentence; relying on the everyday rivalry-preposition without checking the fixed expression leads here by mistake.

• “on” is used when “compete” is followed by an activity or basis (e.g., compete on price), not a person; here the blank is directly followed by a person (“their opponents”), so this preposition mismatches the sentence.

Therefore, “with” is the correct preposition: “...compete with their opponents on equal terms.”