In the speaking part of the Cambridge exams, you will get more points for variety of relevant vocabulary and phrases. So, contemplate these:
• I humbly opine (opino humildemente que) that Mr. Sánchez should call a general election (…debería convocar elecciones generales).
• In my humble opinion his government is a hotchpotch (mezcolanza).
• I posit that (postulo/planteo que) …
• To my mind taxes (en mi opinión…) are too high.
• As I see it (según lo veo) ….
So, what do you opine?