BOSTON — It might not be pretty, but Mitt Romney's campaign insists he'll be the last man standing in the Republican presidential field.
"Those guys, it's going to take some sort of act of God to get where they need to be," a top Romney adviser said during a Wednesday briefing with reporters at campaign headquarters. Those at the session insisted on anonymity while discussing campaign strategy.
Top rival Rick Santorum turned that assessment back at his opponent. "What won't they resort to, to try to bully their way through this race?" Santorum said in Lenexa, Kan. "If the governor now thinks he's now ordained by God to win, then let's just have it out."
Romney himself said in a television interview that he's "prepared to fight all the way" to the Republican National Convention in late summer to go up against President Barack Obama in the fall.
"We've got the time and the resources and a plan to get all the delegates, and we think that will get done before the convention," he told CNBC.
Romney lost four of the 10 states that voted on Super Tuesday and won marquee Ohio by less than 1 percentage point. But he's far ahead in the race for convention delegates, a point repeated by top campaign aides.
The Romney campaign's bottom line: It's going to be a long, hard-fought spring. And while he might continue to make mistakes and struggle to unite voters and the GOP establishment behind him, Romney is, in the words of one adviser, "ahead of the other guys."
In a memo to reporters, the Romney campaign said Tuesday's voting "dramatically reduced the likelihood that any of Gov. Romney's opponents can obtain the Republican nomination."
Romney's six wins increased his lead in the delegate race much more than popular vote totals indicate, the memo said. He now has 415 delegates to Santorum's 176 delegates, according to an Associated Press tally.
Romney's campaign says Super Tuesday was the final opportunity for his rivals to surpass him in delegates.
But senior aides on Wednesday wouldn't identify any upcoming state where Romney is likely to win. Next up are contests in Kansas, Alabama and Mississippi – conservative states where he could struggle. There's a potential bright spot in Illinois, where a special political action committee that supports him is already airing TV ads.
Romney faces the extended calendar with a smaller financial advantage than the one he enjoyed through the campaign's early months. He announced Wednesday that he raised $11.5 million in February, but rival Santorum has said he brought in more than $9 million. Romney was able to close significant gaps with Santorum in places like Ohio and Michigan by spending significant amounts of money on TV ads.
Romney also has acknowledged making a series of campaign mistakes and has said he is working to improve as a candidate. In the CNBC interview, he acknowledged that it's impossible to know whether his plan to cut marginal tax rates by 20 percent will add to the federal deficit.
"It can't be scored," Romney said. He said details still need to be worked out with Congress.
Romney also shifted his position on the minimum wage this week, telling CNBC that "there's probably not a need to raise the minimum wage." Earlier this year, Romney said he hadn't changed the position he held when he was governor of Massachusetts, which is that the minimum wage should rise automatically along with inflation.
Romney took a break from campaigning Wednesday and spent the day at home in Massachusetts.