The ruling party will have to put its own house ...... order.

ANS:A - in

Preposition into is used to when an action is in progress, and in is when action is committing.

And the meaning of this sentence is "the ruling party should make good measures to rule and emphasize its strength among people" and this action is in future tense so we have use in as preposition here, into come when it is in present tense.