Republican presidential nominee Mitt Romney and his running mate, Paul Ryan, hit the road again together Tuesday, this time on a bus tour through the battleground state of Ohio on the heels of a new Washington Post-ABC News poll that shows President Obama surging ahead of them in the Buckeye State.

At an outdoor event in the Dayton suburb of Vandalia on Tuesday afternoon, Romney and Ryan rallied supporters together with Sens. Rob Portman (R-Ohio) and Rand Paul (R-Ky.).

“Look, President Obama — the economy is barely growing. He’s run out of ideas. And just the other day on TV, he said that he can’t change Washington from the inside,” Ryan told the crowd as he introduced Romney.

“Why do we send presidents to Washington in the first place? I mean, isn’t that what we’re supposed to do? Don’t we send them to fix the mess in Washington? Look, if he can’t change Washington, then we need to change presidents,” he continued to cheers and applause.

Romney told the crowd that Obama’s vision for the country is “entirely foreign to anything this nation has ever known.”

He took aim at Obama for backing “the idea of a larger and larger government taking more and more from the people, intruding itself in your relationship with your doctor, investing, so to speak, in companies, picking winners and losers or, in his case, losers.”

At the rally and on the TV airwaves, Romney has sought to cast Obama as too lenient on China when it comes to the valuation of that country’s currency and the shipping of U.S. jobs overseas.

Obama spokeswoman Lis Smith responded in a statement by charging that Romney “is apparently trying to remake himself as a China trade warrior. But if his record is any indication, the voters of Ohio should be very wary of Romney’s empty promises on China.”

“Just a few years ago, Romney said that the President’s decision to stand up to China on behalf of American workers in the tire industry was ‘protectionism’ and ‘decidedly bad for the nation and our workers,’ ” Smith said. “In the private sector, he invested in companies that shipped American jobs to China. And we now know that, for years, Mitt Romney has invested in Chinese companies and profited off of their success. When it comes to China, Mitt Romney isn’t a trade warrior, he’s a paper tiger.”

The Tuesday afternoon rally, which followed a solo Ryan event in Cincinnati, marked the first time the nominees had appeared together since just after last month’s GOP convention in Tampa.

The tour comes as a new Post-ABC poll shows Obama leading Romney 52 percent to 44 percent among likely Ohio voters. The survey not only shows Obama taking a lead in the race for Ohio’s 18 Electoral College votes, but it also suggests that voters’ opinions have hardened six weeks out from Election Day. Eighty-five percent of likely Ohio voters who plan to vote for Obama and 86 percent who are backing Romney say they’ll “definitely” vote for their chosen candidate.

That means that the campaigns’ ability to energize their respective bases could matter more than whether they’re able to woo the relatively small number of undecided voters. It also helps explain why the Romney-Ryan ticket enlisted Paul, a tea party favorite, to join them at Tuesday’s event.

Vandalia is in Montgomery County, which voted 52 percent to 47 percent for Obama over Sen. John McCain (R-Ariz.) in 2008.

At a solo campaign event in Lima, Ohio, on Monday, Ryan took aim at Obama on foreign policy, casting blame on the president for looming bipartisan defense cuts and telling a crowd that the current unrest in the Middle East “reminds you of 1979 Tehran,” referring to the seizure of the U.S. Embassy there and the 52 Americans who were held hostage for 444 days.

Romney joined Ryan in Ohio after his address to the Clinton Global Initiative in New York. Meanwhile, Obama was in New York to address the United Nations.

In his remarks to the Clinton Global Initiative, Romney did not mention Obama, although he used his speech to suggest that the current U.S. foreign aid system has failed.

“I became convinced [while traveling abroad for Bain Capital] that the crucial difference between these countries wasn’t geography,” Romney said.

“I noticed the most successful countries shared something in common,” Romney continued. “They were the freest. They protected the rights of the individual. They enforced the rule of law. And they encouraged free enterprise. They understood that economic freedom is the only force in history that has consistently lifted people out of poverty — and kept people out of poverty.”

Romney in recent days has shifted his criticism of Obama from domestic to foreign policy, perhaps sensing an opening in the wake of this month’s attacks on U.S. diplomatic missions in the Middle East. Democrats, by contrast, have zeroed in on domestic issues, including GOP proposals to cut taxes for wealthier Americans and Romney’s decision not to release more of his tax returns.

In a conference call with reporters Monday, Romney adviser Ed Gillespie dismissed criticism that the campaign has not been focused enough on a single message.

“We are talking about the economy and the need for more jobs and more take-home pay, and we have been talking about that for some time. . . . We are going to comment on the news of the day to the extent that it warrants a response. We try to keep it consistent, choice versus referendum,” Gillespie said.

Democrats, meanwhile, are kicking off their own bus excursion — the “Mitt Romney: Writing Off the Middle Class” tour, which will shadow Romney and Ryan in Ohio.

The tour, led by former Ohio governor Ted Strickland (D) and Brad Woodhouse, communications director for the Democratic National Committee, will remind voters of comments Romney made at a closed-door fundraiser regarding the “47 percent” of Americans who don’t pay income tax and see themselves as “victims” entitled to government help.

Obama is scheduled to be Ohio on Wednesday for events in Bowling Green and Kent.

Nia-Malika Henderson and Rachel Weiner contributed to this report.