But the thin margin of victory could complicate the task of governing for Mr. Maduro, emboldening the political opposition and possibly undermining Mr. Maduro’s stature within Mr. Chávez’s movement.
His opponent, Henrique Capriles Radonski, refused to recognize the results, citing irregularities in the voting and calling for a recount.
Mr. Maduro, the acting president, narrowly defeated Mr. Capriles, a state governor who ran strongly against Mr. Chávez in October. Election authorities said that with more than 99 percent of the vote counted, Mr. Maduro had 50.6 percent to Mr. Capriles’s 49.1 percent. More than 78 percent of registered voters cast ballots.
There were also signs that the strident, Chávez-style anti-American message that Mr. Maduro used during the campaign would now be set aside to improve Venezuela’s strained relations with the United States.
With his election victory looking likely, Mr. Maduro sent a private signal to Washington that he was ready to turn the page. Bill Richardson, the former governor of New Mexico, who was in Caracas as a representative of the Organization of American States, said in an interview that Mr. Maduro called him aside after a meeting of election observers on Saturday and asked him to carry a message.
“He said, ‘We want to improve the relationship with the U.S., regularize the relationship,’ ” Mr. Richardson said.
The foreign minister, Elías Jaua, met with Mr. Richardson on Sunday, and said Venezuela was ready to resume the talks that it had cut off, Mr. Richardson said.
His supporters say that Mr. Maduro lacks his predecessor’s sharp political instincts and magnetism, and many questions remain about how effectively he will lead at home and abroad.