Here is some interesting commentary on McCain's possible difficulties with Romney in Michigan by Detroit News and National Review columnist Henry Payne (thanks to EFM for the scoop):

John McCain played the spoiler in 2000, upending frontrunner George W. Bush in the February Michigan primary and momentarily casting doubt on Bush's party coronation.

As 2008 looms, McCain is the frontrunner--and, ironically, Michigan could prove his undoing.
That's because McCain's chief challenger in '08 is likely to be Massachusetts governor Mitt Romney. With pro-life, pro-military pedigrees, both will appeal to the party base so crucial to winning GOP primaries (exit Rudy G). But as much as Michigan is war hero McCain's kind of state, it's also friendly territory to Romney. The Michigan Republican Party has already split between these two lions, with powerbrokers like AG Cox (McCain) and House speaker Deroche (Romney) marking territory.

Here's why the smart money is on Mitt in the mitt-shaped state:
Start with name recognition, so crucial to McCain's success in 2000. The Romney name is gold here, as Mitt is son of popular former guv, George (that family history should also put to rest the "Will America elect a Mormon?" rhetoric: if Michigan could elect a Mormon three times in the 1960s, why not the nation?).

Mitt is also charismatic. His campaign organization has been quietly seeding Michigan in recent months, and the money folks here are impressed. He has that something that can't be taught: the ability to dominate a room the moment he enters it. Contrast that to McCain, a prickly personality whose stubborn streak often alienates.

Then there's that governor thing. Governors from Reagan to Clinton to Bush have dominated recent presidential elections. And they have defeated top senators like Dole and McCain and Kerry along the way. Why? Because governors have a better feel for America beyond the beltway--a culture McCain has been captive to for a long time.

Romney has also succeeded in the toughest of climates. First, as a brilliant CEO in the U.S.'s demanding capital markets. Then, as a Republican governor in that bluest of states, Massachusetts.

Finally, there's legislation. In just one term, Romney has gained a reputation as a top governor, crafting bipartisan health care reform plan (with Heritage Foundation input) that is one of the country's most talked-about policy experiments. By contrast, McCain's signature legislation, bipartisan campaign finance reform, has been a dud.

Like another handsome, jet-black haired GOP governor from a lefty state, Mitt Romney may ride Michigan's famous "Reagan Democrats" all the way to the White House.