The system we used favored the moderate. Too many conservatives had them splitting the vote, and when added with the winner-take-all system, that meant they slowly had to drop out.
Better a system of primary delegates apportioned proportionally state-by-state. They'd still be splitting the vote, but they wouldn't be getting so far behind, either.
A conservative caucus within the party would also help. They would endorse up to only 2 or 3 true conservative candidates per primary season.
Trust me, it will work out if conservative like Bobby Jindal gets into the primaries. When there is a real conservative, primaries will be over soon. People like him have huge organizational skills and work in building the party at local levels.