VANDALIA, Ohio — Ohio has emerged as the presidential race’s undisputed focus. Barack Obama and Mitt Romney are making multiple stops this week alone in a state that’s trending toward the president, endangering Romney’s White House hopes.

The popularity of Obama’s auto industry bailout and a better-than-average local economy are undermining Romney’s call for Ohioans to return to their GOP-leaning ways, which were crucial to George W. Bush’s two elections. Ohio has 18 electoral votes, seventh most in the nation, and no Republican has won the White House without carrying it.

Romney is scrambling to reverse the polls that show Obama ahead. On Tuesday, he made the first of his four planned Ohio stops this week, joining his running mate, Rep. Paul Ryan, for a rally near Dayton. Today, Obama will visit the college towns of Kent and Bowling Green, and Romney’s bus tour will stop in the Columbus, Cleveland and Toledo areas.

“If this president persists on the road of making it harder and harder for small businesses to grow and thrive, he’s going to slowly but surely weaken our economy and turn us into Greece,” Romney said Tuesday in Vandalia. He said the Obama administration has put government between patients and their doctors, and is picking winners and losers in private business.

“That is not the America that built Ohio!” Romney declared.

His tone was urgent, but the points were standard campaign language from Romney. His allies hope they will start resonating in this crucial state.

Not even Florida has seen as many campaign ads as Ohio, and neither nominee goes very long without visiting or talking about the state. When Obama touted his “decision to save the auto industry” on CBS’ “60 Minutes” on Sunday, he mentioned not the major car-making state of Michigan but Ohio, which focuses more on car parts. “One in eight jobs in Ohio is dependent on the auto industry,” Obama said.

Four new polls underscore Romney’s serious problems in Ohio. Surveys by NBC and Fox News found Obama ahead by 7 percentage points. A poll by a group of Ohio newspapers showed him leading by 5. And a Washington Post poll released Tuesday found the president leading Romney by 8 points. All of Obama’s leads were outside the polls’ margins of error.

One problem for Romney is that Ohio’s 7.2 percent unemployment rate is below the national average, as the Republican governor, John Kasich, often reminds residents. “We are up 122,000 jobs,” Kasich told a panel during the Republican convention last month. “The auto industry job growth is 1,200,” he said, perhaps trying to play down that sector’s role.

Kasich said he supports Romney and Ohio would do even better if Obama were replaced. But the governor’s understandable pride in the state’s job growth runs counter to Romney’s message that Obama is an economic failure.

House Speaker John Boehner, from the Cincinnati area, said last week in Washington: “One of the things that probably works against Romney in Ohio is the fact that Gov. Kasich has done such a good job of fixing government regulations in the state, attracting new businesses to the state.”