And, Romney acknowledged that his own mistakes aren't helping.
Asked by reporters why he's struggling to win over his party's right wing in the state where he was born and raised, Romney said it's because he's not willing to say "outrageous things" like his opponents.
"It's very easy to excite the base with incendiary comments. We've seen throughout the campaign that if you're willing to say really outrageous things that are really accusative and attacking of President Obama, you're going to jump up in the polls," Romney said. Fielding questions from the national traveling press corps for the first time in nearly three weeks, he said: "I'm not willing to light my hair on fire to try and get support. I am what I am."
And asked if remarks highlighting his wealth -- like when he said Sunday he doesn't follow NASCAR as closely as some but has "great friends who are NASCAR team owners" -- were hurting his campaign, Romney said: "Yes. Next question."
Romney also accused Santorum of trying to "kidnap the primary process" by urging Democrats to come to the polls in Michigan's open primary and vote against the former Massachusetts governor.
Santorum's campaign is calling Democrats in Michigan, urging them to vote in Tuesday's GOP primary, which is open to members of other parties. The call urges them to vote against Romney because he opposed the government bailout of the auto industry.
Romney himself voted in Democratic primaries in Massachusetts in an effort he says was aimed at picking the weakest opponent for the Republican who was running. He said Tuesday he voted "against Ted Kennedy, Tip O'Neill and Bill Clinton," and that doing so as a private citizen was different than a presidential campaign paying for phone calls.
Both campaigns are waging all-out efforts to bring supporters to the polls because the race between Romney and Santorum in Michigan is neck-and-neck.
Romney has acknowledged that a loss in the state where his father served as governor would be hugely embarrassing and could deal a strong blow to his campaign.
The former Massachusetts governor spent the past five days campaigning hard in Michigan, selling himself as a native son steeped in the auto industry that has defined the state for decades. He has a strong lead in Arizona, which also votes Tuesday.
Romney has recently pivoted away from the cultural issues that the outwardly religious Santorum has brought to the forefront of the campaign. He had been attacking the former Pennsylvania senator as not conservative enough, but on Monday focused instead on the economy. On Tuesday, Romney called Santorum an "economic lightweight" who isn't prepared to fix nation's economic woes.
"I am running against a guy in this state who is an economic lightweight. He doesn't understand how the economy works," Romney told supporters Tuesday.
Romney was forced to play catch-up in Michigan after losses to Santorum on Feb. 8 in Minnesota, Missouri and Colorado. While still leading in delegates, Romney fell back in polls. A loss in Michigan would seriously damage the campaign of the on-again, off-again front-runner and probably stretch an already lengthy GOP nominating contest even more.
Romney claimed Tuesday that he doesn't see his campaign organization as responsible for his setbacks -- instead, he blamed himself.
"I'm very pleased with the campaign, its organization. The candidate sometimes makes some mistakes and so I'm trying to do better and work harder and make sure that we get our message across," Romney said.
Even if he loses in the state, Romney can still pick up a significant number of delegates in Michigan. The state awards two delegates in each of the 14 congressional districts.
The Michigan fight has tightened in recent days as Romney's campaign and its wealthy super PAC allies have attacked Santorum in TV ads. Romney has been attacking Santorum's credentials as a conservative, while the former Pennsylvania senator has told voters that Romney can't be trusted to uphold socially conservative principles.
Romney and his allies now turn their attention to the 10 states that vote March 6, Super Tuesday. Romney's campaign bought more TV airtime for ads in Ohio while the super PAC Restore Our Future plans to spend more on TV ads in Ohio, Tennessee, Georgia and Oklahoma.
Romney will stop in Ohio on Wednesday before flying to North Dakota and then on to Idaho. All three hold vote March 6.