“But I also think we’ve learned that our troops shouldn’t go off and try and fight a war of independence for another nation,” he said. “Only the Afghanis can win Afghanistan’s independence from the Taliban.”

On Tuesday, Mr. Romney sought to draw a distinction between his thinking and that of Mr. Huntsman and others who say the financial cost should be a big factor in the calculation.

“There will be some who argue it’s too expensive now, we’ve got to bring the troops home right now, or others will say, politically we need to make one decision or another,” Mr. Romney said here. “You don’t make a decision about our involvement in a conflict based on dollars and cents alone or certainly not with regards to politics.”

Tim Pawlenty, a former governor of Minnesota, said that conditions on the ground and the advice of military commanders — not the cost — should guide decisions about Afghanistan troop levels.

“We have to remember why we invaded the country in the first place,” Mr. Pawlenty said, adding that the security level was not yet sufficient for a full withdrawal. But he said, “Our mission in Afghanistan is not to stay there forever or to stay there for 10 more years to rebuild their country.”

The array of Republican viewpoints, which have drawn new lines among neo-conservatives, Tea Party supporters, traditional hawks and other elements of the party, were on display during the first major presidential debate on Monday night, as the candidates started to mull the limits of American power at a time when some of the threats to the nation are less clear and its willingness to commit resources of all kinds is being looked at anew.

Representative Michele Bachmann of Minnesota, a member of the House Intelligence Committee, said the decision by Mr. Obama to involve the United States military in the effort to dislodge Col. Muammar el-Qaddafi from power in Libya was “substantially flawed” and did not meet the criteria of protecting the national interest.