But their incentives have also shifted for other reasons — the proliferation of super PACs, because of increasingly relaxed campaign finance rules, coupled with the large GOP field. Candidates are spending more time courting donors, such as the visit several made last weekend to meet contributors at Mitt Romney’s retreat in Utah. In 2012, GOP candidates continued to compete deep into the primary calendar beyond Iowa and New Hampshire thanks to well-funded super PACs.

Republican consultant Tim Albrecht of Iowa, who once worked for Romney, said the winnowing process “will be a lot longer, too, because of super PACs, if nothing else.”

Much of the criticism has been directed at Fox News and its decision to limit the debate to 10 GOP candidates.

Ayotte’s comments follow protests last week from 56 members of the New Hampshire Republican elite who wrote a letter to Fox News to argue its debate was antithetical to the spirit of the nominating process. And on Wednesday, more than 100 elected officials in South Carolina sounded a similar alarm, saying the debate “undercuts the historic role of South Carolina and other early states.’’