Step 1: Understanding the Concept:
Understanding the figurative meaning of the English idiomatic expression 'to blow hot and cold'.
Step 2: Detailed Explanation:
The idiom 'to blow hot and cold' means to vacillate constantly in one's opinions, being enthusiastic and supportive at one moment and hostile, indifferent, or opposing at another.
Replacing it with 'supports and opposes' (inconsistent vacillation) preserves the exact semantic sense.
Step 3: Final Answer:
Therefore, 'supports and opposes' suitably replaces the phrase.