Was the MI primary only for President? Because if it was only for President then, yes, the turnout is a good sign for Clinton.
On the other hand, if there were also primaries for other races on the ballot, it's entirely possible that people came out to vote for those races, and, seeing only Clinton, Kucinich, and Gravel on the ballot, just voted for Clinton as an afterthought.
Most of the ones without candidates, I can hardly blame people for not bothering with them. But we really should have candidates -- good ones -- in the California 25th; the Florida 18th; the Michigan 4th, 6th, 8th, and 10th; and the Virginia 4th.
There was no "hard-fought race" in 1960. Rockefeller never officially joined the race, then he announced that he was out altogether. Nixon ran unopposed.
Goldwater won by a landslide over Rockefeller in '64. The only significant state primary that Rocky won was Oregon, where no other candidate bothered to show up. Goldwater had a much more potent challenge from Henry Cabot Lodge, Nixon's 1960 running mate.
In 1968, it may have been Rockefeller's turn again, but since he ran as a write-in candidate against the former Vice President of the United States, that didn't help much. Your "turn" will only get you so far.
Reagan lost in 1976 because it was Ford's turn. Ford was the sitting President. It is always the President's turn first, no matter how many people really dislike him. See: 1992.
In 1980, you had Ronald Reagan, the former Governor of California, charismatic, conservative, and due for the nod, because of his earlier races. An unbeatable combination.
1988 is, next to 1996, the clearest instance of someone taking his turn. Voters didn't like Bush. They were much more drawn to Dole on the one hand and Robertson on the other. For about five seconds. You'll notice that after Iowa, Bush won almost everything there was to win.
Bush didn't win a "less-than-convincing" victory, it was a blowout. Buchanan kept it close in one state, and he lost that.
1996 was clearly decided based on whose turn it was. Republican voters looked over the primary field, passed over popular, fresh-faced candidates aplenty, and picked an old, tired, unpopular Washington insider who had run twice before and earned his turn at the brass ring.
In 2000, yes, there was no one with a clear "turn" for the nomination. So who did the voters settle on? A maverick? A wealthy self-funder? The former Vice President? No, they picked George Bush, just like they did in '88 and '92. Hey, he was a Bush. And they knew what they'd get with that, right?
Sizemore was found guilty of racketeering and money laundering in civil court over one of his groups. Now, I know wingers are a little nutty, but would they really put a "racketeer" up as their primary challenge to an incumbent U.S. Senator?