“You can’t treat this like a math equation... What is Mitt asking people to be part of?”

But the challenges for Mr. Romney, particularly the dogfight with Mr. Santorum in Ohio despite a significant financial advantage, touched off alarm among several donors and supporters. Some complained in interviews that the campaign had yet to devise a strong, simple and sound-bite-friendly economic plan with broad appeal, which could rival Mr. Gingrich’s relentless focus on high gas prices.

Mr. Romney’s victory in Ohio appeared to have quelled outside speculation that he would have to shake up his campaign staff. Yet it did little to tamp down criticism that he was failing to provide an overarching, inspiring vision, which was underscored by his aides making the argument that Mr. Romney would win based on the clinical work of delegate accumulation.

“You can’t treat this like a math equation,” said Alex Castellanos, a political adviser to Mr. Romney during his 2008 campaign. “Your job as a candidate is to inspire people to join something greater than ourselves. What is Mitt asking people to be part of?”

Several campaign aides acknowledged that fatigue had settled in for both the candidate and his staff here in Boston. One adviser, speaking on condition of anonymity, said Mr. Romney had too often resorted to micromanaging, especially on speeches and opinion pieces for newspaper editorial pages.