The only reason he’s ahead is because he’s poured $5.7 million of his own money into the race. He was the first candidate in general to start advertising, before any other Democrat or Republican. Considering he said that he was only running to piss off the establishment, he had to have changed his mind, as nearly $6 million is not chump change.
Brian Calley just recently started running ads, while the GOP frontrunner, Bill Schuette, hasn’t started yet. It appears that both Whitmer and Schuette are both hoarding cash to prepare for a food fight in the general election, both just assuming that they can Hillary Clinton their way to their party’s nominations over the objections of their respective party bases.
I also think that its still early / not too late to spend the money for the primary. June and July will be when the races are won.