By Sam Youngman
BEXLEY, Ohio (Reuters) - Republican presidential candidate Mitt Romney appealed for the support of working-class Americans in industrial Ohio on Wednesday, a day after narrowly averting a humiliating defeat by rival Rick Santorum in Romney's home state of Michigan.
Romney focused almost exclusively on the U.S. economy, China and stiff criticism of President Barack Obama's leadership at his first campaign events after Tuesday's Michigan primary.
"The reason I won yesterday in Michigan and Arizona is because I'm talking about the issue people care most about and I understand that issue," Romney said at a rally in Bexley, outside the state capital of Columbus.
"Rick Santorum's a nice guy, but he's an economic lightweight," said Romney, who made a fortune as a private equity executive.
Ohio, one of 10 states to hold primaries or caucuses on "Super Tuesday" next week, is a politically divided state that will be crucial in the November election, when the Republican nominee will face Democratic President Barack Obama.
Romney has reclaimed front-runner status in the state-by-state race for the Republican nomination but to solidify that standing - or avoid losing it - he must win Ohio over his chief rival: the former senator from Pennsylvania Santorum.
Romney also rolled to an easy victory in Arizona on Tuesday, but all eyes were on Michigan, where Santorum, known for his religious conservatism, posed an unexpectedly stiff challenge. Romney's margin of victory was only 3 percentage points in the state where he grew up and where his father was governor in the 1960s.
Santorum won about half of Michigan's 30 delegates with his strong second-place finish. Spending the day campaigning in Tennessee, he claimed victory in Michigan and promised to fight on for the nomination.
"We're doing battle, we'll be there (Ohio) a couple of times this week. We're going to be in Tennessee, Oklahoma, Washington state and Georgia - we're going to compete, and we're going to do exceptionally well on Super Tuesday," he said on Fox News.
Washington state holds its caucuses on Saturday.
Tuesday's results were enough to ease pressing concerns about Romney's ability to win over the conservative Republican base and solidify his lead among Republicans.
But the slim margin of victory made clear that the party could face a long slog before anointing its presidential candidate. Republican leaders worry that an extended, acrimonious primary battle will damage the eventual nominee. Romney's approval ratings have fallen as the race has heated up.
Republicans are particularly concerned about Ohio, a swing state they believe is a must win if they are to take the White House. The primary in the diverse state will also gauge both Romney and Santorum's ability to draw a broad range of voters.
ECONOMY, CONTRACEPTION AND GUNS
Focusing on the economy should help.
Gallup poll data showed registered U.S. voters rate the economy the most important issue in the 2012 presidential race, followed by jobs, the budget deficit and Obama's healthcare law. Social issues were least important.
"I've always leaned toward Romney instead of Santorum," said Susan Howard, of Bexley. "I definitely want to hear about the economy, taxes, Obamacare. The (social) issues will fall into place. Getting people back to work, that's the key for me."
The fervently Roman Catholic Santorum has appealed to the religious right with his stands against gay rights and contraception. Adding a populist economic message tied to his working-class roots as the grandson of a coal miner, he has led in nationwide polls since winning contests in Missouri, Minnesota and Colorado on February 7.
Exit polls on Tuesday showed Romney had strong support from wealthier voters and those over 65.
Santorum carried the most conservative voters, those who said the religious views of candidates were important and those who were less affluent and educated.
The Harvard-educated Romney, who has a personal fortune estimated at some $250 million, has struggled to connect with blue-collar voters, making a series of gaffes such as offering at $10,000 bet that served as reminders of his vast fortune.
His centrist record as governor of Massachusetts also worries some conservatives, while some evangelical Christians view his Mormon religion as a cult.
On Wednesday, Romney may have misstepped again, by replying when asked about gun control that he had guns himself, but would not say where. "Not going to tell you where they are," he said. "Don't have them on myself either."
Opposition to gun laws are a litmus test in U.S. Republican politics and Romney ran into trouble while campaigning in 2007 by saying he owned guns and then had to retract when it turned out they belonged to his son.
Earlier on Wednesday, Romney visited the a fence post factory in Toledo, Ohio, where he told about 100 people, "I want to go to work for the American worker."
(Additional reporting by Susan Heavey and Patricia Zengerle in Washington and Steve Holland in Detroit; Writing by Patricia Zengerle; Editing by Doina Chiacu and Christopher Wilson)