It wasn't supposed to be this hard.

As the Romney campaign chieftains looked at the path to the Republican nomination last year, they never envisioned a struggle to win the candidate's home state of Michigan.

However, a battle plan and the realities of war are rarely in concert with one another.

Few successful presidential nominees in the modern era have gotten to be the party's standard bearer without facing down a significant and potentially mortal threat.

Mitt Romney did just that tonight. But it wasn't pretty.

"We didn't win by a lot, but we won by enough. And that's all that counts," Romney told a room full of supporters Tuesday night in Novi, Mich., celebrating his dual victories in Arizona and Michigan.

Romney continues to rack up the delegates needed to secure the nomination, but he has done little to put to rest the concerns within his party that the process has not been kind to his standing with the American electorate, specifically the independent voters who will decide the election in November.

But what Romney did accomplish on Tuesday night is significant. His victories will invite more money into his campaign coffers, more establishment Republicans to endorse him, and a lot more questions about his opponents' abilities to deny him the nomination.

Most important, the Romney victories on Tuesday will significantly dampen the increasingly loud chatter of late that the Republican Party might need a white knight (Mitch Daniels, Paul Ryan, Chris Christie, Jeb Bush) to come in and save the day.

Romney's weaknesses become clear with each passing primary night. In Michigan, the only income group he won was among voters earning more than $100,000 per year. He still can't get the heart and soul of the Republican Party — the very conservative voters — to warm to his candidacy. And evangelical Christians remain unenthused.

Despite those holes in the support of his base, Romney made clear tonight he is going to keep his eye on November with a more broadly appealing economic message.

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"More jobs, less debt, smaller government — we're going to hear that day in and day out," he said. "I stand ready to lead our party to victory and our nation back to prosperity."

And Romney wasn't the only candidate signaling a decision to move away from the recently dominant campaign trail talk on issues like contraception, abortion, and the separation of church and state.

Rick Santorum began his final pre-Super Tuesday push in a speech that started with his highlighting his 93-year old mother's college and post-college education (the kind of education for which he called President Obama a "snob" for encouraging) and her work outside the home as a nurse during Santorum's childhood.

It was clear in his remarks that Santorum was eager to begin to repair the damage he believes has been done to his image by having his campaign defined by his stances on social issues.

The candidates have seven days to make their closing arguments to voters in 10 states before the polls close on Super Tuesday. It is the largest single-day delegate prize of the nomination season.

Certainly a lot of focus will now be placed on the Romney vs. Santorum battle in Ohio. It is yet another Midwestern battleground state, but this time without the added benefit of a home-field advantage for either candidate.

But Romney's victory in Michigan will likely be viewed as the critical moment in the 2012 contest should he accept his party's nomination in August in Tampa.

As long as wealthy individuals remain committed to funding pro-Santorum and pro-Newt Gingrich super PACs, this contest will drag on beyond Super Tuesday, but if Romney racks up significant victories next week (both in number of states won and in number of delegates), the law of diminishing returns will begin to take its toll on his competitors.

Romney took a big step tonight toward becoming the Republican Party's presidential nominee. It just remains unclear when he will be able to earnestly begin the work of undoing the serious damage that has been done to him in the eyes of the larger American electorate.

David Chalian is the Washington bureau chief for Yahoo News.

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