That's an odd notion. Maybe you need to properly define 'ideas' here, because a terribly vague thing you are saying here. I took it that you are talking about policy ideas here, which is something we only know about because people speak them out loud. Frankly, we don't know the exact ideas in a person's head, so we cannot judge them on these merits alone.
Behavior, we can judge. Past actions, we can judge. But just because someone says 'we should reduce taxes to stimulate growth' doesn't mean we know exactly what ideas drive them, even if your hypothesis is to be taken at face value. If a known liar who has shown to be more interested in being in power than doing good for their country says that, then that should be taken into account as well.
You can debate ideas on their own, that is fine. But if you debate who to vote for, then focusing solely on some ideas a candidate espoused seems foolish.