Already, the Independent Liberal Party has accused Mr. Ortega’s party of scheming to pick up votes by denying identification cards to critics of the government, while granting them to Honduran citizens working along the border. (The government disputes the allegations.)

And many still resent Mr. Ortega’s political maneuvering to permit his re-election. The Nicaraguan Constitution bars leaders from serving consecutive terms and limits their total service to two terms. But Nicaragua’s Supreme Court, which Mr. Ortega controls, ruled in 2009 that the limits violated human rights.

“If the candidate is in the people’s interest, they will elect him, and if the candidate does not represent their wishes, they will not elect him,” Mr. Ortega said in a rare television interview that year. “Obstacles should not be set up to deny them that right.”

The United States cut about $62 million in aid over concerns about the 2008 elections but has otherwise largely let Mr. Ortega be, wary of provoking anti-American sentiment.

“He goes to the precipice, but he doesn’t jump off,” explained Robert J. Callahan, who stepped down as the American ambassador to Nicaragua in July. “He does just enough to allow the community of democracies to justify staying and attempting to work with him.”

Mr. Callahan said that if there was evidence of widespread fraud in the elections, the United States should cut off future economic aid to the country, refuse to name a new ambassador and forcefully condemn Mr. Ortega. In a statement, the State Department said it remained concerned about the potential for voting irregularities.

Some Nicaraguans, even those who support Mr. Ortega, said his barbed language had isolated the country. “He has worsened the relationship unnecessarily,” said Álvaro Maradiaga, 20, an architecture student from Managua who hopes to spend time in the United States. Nevertheless, Mr. Maradiaga said he would vote along party lines for Mr. Ortega.