Updated 5:55 p.m. ET
PERRYSBURG, Ohio - Rick Santorum's final pitch on the day of the Michigan primary was aimed not just at Republicans, but at the proverbial "Reagan Democrats" who swept his Republican hero into office in the 1980s.
At a rally with several hundred supporters, Santorum said his message of increasing energy production and revitalizing manufacturing was one that would appeal to conservative Democrats - hopefully those in Michigan, where voters were going to the polls on Tuesday. It's a message that will also carry well into blue-collar Ohio, where Santorum has already done multiple events ahead of the state's March 6 primary.
"It's a message that is playing well, hopefully very well, today in Michigan. And it's a message -- it's a message that we're selling to not just Republicans, but Republicans and Democrats - Reagan Democrats, who are the key for us winning Ohio, and Pennsylvania, and Michigan back in the day when Ronald Reagan represented a Republican Party that stood for all of the values that made this country great," Santorum said.
The term "Reagan Democrats" was coined to describe traditionally Democratic voters, especially white working-class Northerners, who defected to support Reagan in both the 1980 and 1984 elections. Trying to win over those Democrats - who could help hand Santorum a narrow win over his GOP rival Mitt Romney in Michigan - is the rationale his campaign has been providing for sending a robo-call to Democrats in the state.
Romney - who the robo-call targets, reminding voters that he opposed the auto bailout of Detroit - has labeled the strategy "a real effort to kidnap our primary process."
Santorum responded by calling Romney a "bully."
"That's what bullies do -- you hit them back, and they whine," he told reporters after the rally. He said Romney had no trouble with non-Republicans voting in New Hampshire, where they made up 53 percent of the electorate.
But Santorum himself has objected in the past to Democrats participating in GOP primaries. In a telephone town hall in late January, Santorum said, "We want the activists of the party, the people who make up the backbone of the Republican Party to have a say in who our nominee is, as opposed to a bunch of people who don't even identify themselves as Republicans picking our nominee," Santorum said then. "I don't like that. I believe that states should only allow Republicans to vote in Republican primaries."
Romney spokesman Ryan Williams, who attended Santorum's event, said, "Senator Santorum obviously doesn't want to discuss his robo-calls today. He got called out on them and is making dishonest comparisons between his outreach efforts to President Reagan."
Williams also noted that the New Hampshire primary is open only to Republicans and independants, meaning Romney's support came from those groups. Democrats could not have voted for Romney in that primary, he said.
Santorum's final stop before the Michigan polls closed was his Grand Rapids headquarters, where he and his wife, Karen, called supporters and spoke to reporters.
Responding to a charge from Romney that he is an "economic lightweight," Santorum turned the charge on his head and called Romney a "lightweight on conservative accomplishments."
And Santorum again appealed to working-class voters by portraying himself as one of them.
"I'm not a multi-millionaire," Santorum said, although he fact earns about $1 million a year through his consulting business and real estate holdings. "I'm someone who has gone out and worked hard and learned my economics from shining shoes and working in conferences and setting up conference centers ... "
(Watch Santorum's lighthearted, yet stinging, response to being asked if the Michigan primary is "must win.")
Arden Farhi contributed to this story