WESTERVILLE, Ohio — Speaking to a high school gymnasium full of enthusiastic Republicans, Mitt Romney tried to train their attention on one of the few issues with which he has maintained an advantage over President Obama in the polls: Federal borrowing.

"That clock up there shows our national debt," Romney said, gesturing toward a large sign with a live ticker showing a growing dollar figure around $16 trillion. "When I began this campaign it said it was 15 trillion. I mean, what is a trillion? It's a thousand billions. It's an unthinkable amount!"

The crowd in the high school gymnasium groaned, and Romney plowed on.

"If [Obama] were re-elected I could assure you it would be almost $20 trillion in debt," he said. "And by the way, those debts get passed on to our kids."

The traveling debt clock was a regular prop for Romney during the Republican primaries, and it was prominently displayed at the Republican National Convention. But it has been largely absent from his campaign stops in recent weeks, as Romney has zig-zagged his way through the general election, shifting his message from day to day in an effort to gain ground on Obama. The clock was back Wednesday, along with a large banner that read, "We can't afford four more years."

With a fresh New York Times poll out today that shows Romney with an edge over Obama when it comes to who Ohio voters trust more to handle the budget deficit, the Republican apparently decided to hit the issue hard in his morning rally. (He chose to focus on the more eye-popping national debt, rather than the federal budget deficit exclusively, but most voters seem to conflate the two.)

By focusing on the debt, Romney is trying to play to his strengths. But to win over undecided voters, and win back some reluctant Obama supporters here, the Republican may have to do more than show his superiority on the issue: he'll have to convince Ohioans that this is the issue that should decide their vote. Hence, Romney's efforts to intensify the urgency of the debt with his "thousand billions" remark.

But with the pool of truly sway-able voters shrinking in the state, the Romney campaign may come to realize that a one-size-fits-all message — event on an issue where their candidate excels — won't do the trick.

Tracy Sabetta, an undecided voter from Pickerington, Ohio, said she's "hoping to hear something inspiring from either candidate."

Her top issue?

"I'm very concerned about the Great Lakes," she said.