February was supposed to be Mitt Romney’s month, a time when he could put distance between himself and his rivals for the Republican nomination with a series of contests on generally friendly terrain. Instead it turned into a grinding endurance test far more difficult than anything he or his campaign had imagined.

But on Tuesday night, the former Massachusetts governor did what he had to do. He easily won the state of Arizona — and all its delegates — in a campaign that was not seriously contested by his rivals. And in the big prize of Michigan, he also won — as he desperately had to do. If he did not overcome some of the doubts about his candidacy, he reestablished himself as the favorite to win the nomination.

In Michigan, he defeated former Pennsylvania senator Rick Santorum, but by a relatively narrow margin in a state where he grew up, where his father served as governor and where he won by an even bigger margin in the 2008 primary on his way to losing the nomination.

Tuesday’s results prevented what could have been a calamitous day for Romney. Instead the two primaries provided a tonic for a campaign and a candidate that have been the target of criticism for weeks. Together, Michigan and Arizona helped Romney bounce back after a trio of victories by Santorum on Feb. 7 knocked him off stride.

His Michigan comeback — he fell behind Santorum earlier in the month — showed his resilience as a candidate and underscored the advantages he holds in the nomination battle — more money, a superior organization and the ruthlessness to attack anyone in his path. Still, his advisers fretted that he would not get enough credit for turning around a campaign that only a week ago had party strategists speculating about the possibility of another candidate getting into the race.

Yet even in victory, the campaign in Michigan highlighted Romney’s flaws as a candidate. That he had to fight as hard as he did in a state he won four years ago was a reminder that he is still struggling to connect with a portion of his party’s base, even against what party strategists regard as relatively weak opposition.

While Tuesday reinforced again that he has the clearest path to the nomination, the way he won suggested that he still might have to scratch his way there, which is not how a front-runner is supposed to win.

Romney struggled in the final days of the campaign with gaffes that drew unwanted attention to his wealth and that reinforced concerns among party leaders that he may be turning a perceived strength — his background in business — into a liability among economically stressed voters.

His challenge will be to show that the struggles of February have made him a stronger and more appealing candidate, both to his party’s base and as a potential nominee. His message and demeanor the past two days indicated that he recognizes that he went off track and that, at times, he has compounded his problems with unforced errors.

When he said Tuesday that he had made mistakes and when he admitted that he was not willing to “light my hair on fire” to appeal to the most conservative of Republicans, he seemed to be planting his feet more firmly than he has in the past. But can he stick to that in the weeks ahead?

That opportunity begins in the next week. After a three-week, two-state focus, the four remaining Republican presidential candidates now turn their focus to Super Tuesday and a far larger landscape. There are nearly a dozen contests over the next week spread across all regions of the country and with far more delegates at stake next Tuesday than in all the contests to date.

Romney can anticipate some almost certain victories next week. The battlegrounds include Massachusetts, where he served one term as governor, and Virginia, where only he and Rep. Ron Paul (R-Tex.) qualified for the ballot. His campaign sees opportunities to pick up a good share of the delegates even in states where others may be favored.

At the same time, Santorum and Newt Gingrich see opportunities in Tennessee, Georgia and Oklahoma, where they hope to embarrass the former governor and extend the race indefinitely. Paul hopes to score his first victory in one of several states holding caucuses. Gingrich has said he must win in Georgia. But in general, there appears to be no real incentive for the others to quit the race soon.

The most contested state by far on Super Tuesday will be Ohio, where Romney could find himself in another fierce campaign against Santorum, but without some of the advantages he supposedly held in his home state.

Santorum has been leading in the most recent polls in Ohio, but the candidates will start fresh on Wednesday. In other states, polls have swung wildly based on each week’s results and it’s likely that Ohio’s landscape will be reset by Tuesday’s results.

Santorum will have at one obvious disadvantage in Ohio that did not exist in Michigan: The primary there is open only to Republicans. Michigan’s primary allowed Democrats and independents to participate, and exit polls showed Santorum winning a majority of Democrats and roughly splitting independents with Romney.

How many of those Michigan Democrats were there to create mischief and to hurt Romney isn’t exactly known, but the exit polls showed enough anomalies to suggest that many of the Democrats who did take part in the Republican primary did not do so because they were ideological soul mates with the conservative former senator.

If Romney stumbled at times, Santorum hurt himself even more in the final days of the campaigns in Arizona and Michigan. His missteps included a poor performance in the candidate debate last Wednesday in Arizona and a series of controversial statements. He called President Obama a snob for suggesting that he wants all children to go to college and said former president John F. Kennedy’s 1960 speech on religion and politics made him almost throw up. Overall he strayed far from his intended strategy of talking economics in a hard-hit state.

In his speech to supporters Tuesday night, Santorum appeared eager to put some of those mistakes behind him and to recalibrate his message and rebalance his candidacy. That will be his test going forward.

Given the twist and turns this year, it is difficult to say what chance Romney has to begin to close down the nomination battle after Super Tuesday. No one can see quite that far ahead. As Romney said in summing up the results to supporters Tuesday night, “We didn’t win by a lot, but we won by enough.”