From Flint, Michigan -

At every rally for Mitt Romney that I have covered in Iowa, New Hampshire, South Carolina and Florida, the main music that plays at the end of the event is "Born Free" by Kid Rock.

But over the weekend, the music of that Michigan native was replaced in his home state.

Instead of using someone identified with "8 Mile Road" - a Detroit area landmark matched only maybe by the giant Uniroyal tire on I-94 - Romney's events started using "Dance to the Music" by Sly & The Family Stone.

The musical shakeup came at a time when Romney was scrambling to win a primary in a state where both Romney and his wife grew up and went to high school, a state he won easily in 2008 and one he certainly never thought would be in doubt.

It's a perplexing struggle on many levels, since the Romneys certainly know more about Michigan than Rick Santorum, Ron Paul and Newt Gingrich combined, cubed and squared.

For example, Romney's wife Ann got some cheers at an event in Kalamazoo on Saturday when she mentioned her affinity for "Vernors" - a unique drink that most readers might never have heard of let alone tasted.

"I like to tell people that if you cut us open and we bleed, we bleed Vernors," Romney's wife said to chuckles in the crowd.

I will note that I still shake my head at the peculiar taste of Vernors, which we often had stashed in our basement refrigerator while I was a kid living just outside Detroit.

But Romney the Candidate doesn't trot out too many memories like that of his own boyhood days here, where he attended the prestigious Cranbrook Schools in Bloomfield Hills and watched his father become Governor.

That background combined with the support of Michigan's establishment was thought to be more than enough for Romney in 2012 in his native state.

Instead, he has struggled to overcome Rick Santorum's spirited challenge.

"I care about Michigan, I care about Detroit, I care about Flint and Lansing and Kalamazoo," Romney said at one weekend stop.

"On Tuesday, I need you to vote," Romney added in a direct appeal that sometimes he has shied away from in other states.

"I need you to vote for me," Romney said with a self-effacing smile and chuckle.

It was one of the few moments that the crowd seemed to connect with Romney on a personal level.

During my 350 mile drive back and forth across the Lower Peninsula on Sunday, it wasn't hard to figure out who is on the attack right now, as I heard attack ads against Santorum both by Romney's campaign and the Super PAC allied with him.

Romney's ad tied Santorum to Michigan Democratic Senator Carl Levin - "liberal Senator Carl Levin" as they put it in the ad - arguing that Santorum is a budget-busting closet liberal.

On Monday, Santorum and Romney will be going in opposite directions, as Romney starts his day near Grand Rapids and ends up outside Detroit; Santorum starts in the Detroit suburbs and ends up in Kalamazoo.

On Sunday night, Santorum used an event outside of Flint to jab repeatedly at Romney, especially over his ads that question Santorum's conservative bona fides.

"I get a big kick out of Governor Romney running ads against me that I am not the conservative in this race," Santorum said.

Santorum repeatedly hammered home his argument that he's more conservative on a host of issues than the former Massachusetts Governor, as Santorum accused Romney of being a moderate in disguise.

"He ran to the left of Ted Kennedy," Santorum said, referring to Romney's unsuccessful run for the U.S. Senate, as the former Senator urged his backers to do all they can to bring about a win on Tuesday.

"Michigan will shock the political establishment in Washington, D.C.," Santorum said to huge cheers.

Not long after Santorum finished shaking hands with supporters, a new poll came out showing him trailing Romney by two points, after leading in a number of polls over the last two weeks.

We will find out tomorrow if Santorum has an upset in the making or if Romney's big push has paid off - in a state that many never expected to be this close.