" it seems like being first should rotate a bit."...Amen! I've been saying that for 5-6 years now. There should be a lottery..or a similar system...to rotate the primary schedule each 4 years. It would still 'favor' certain candidates at times, but would sure be an imporvement.
Better yet, NO primaries, but a system of candidate selection thru grass-roots organizations...then a set primary date for everyone where the final candidates are selected. And get money as far out of the way as possible...give every final candidate a budget and strict limits on how it can be spent.

Yeah, there are problems in the details, but it's a direction.