ROME, May 10 — A new Italian president was finally approved on Wednesday, in an untidy parliamentary election that nonetheless cleared the way for Romano Prodi to take office as prime minister.

The choice was Giorgio Napolitano, 80, a member of Parliament for half a century, a former president of the lower house and, until 1989, a leader of the Italian Communist Party. The job is largely ceremonial, and Mr. Napolitano, now a member of the largest center-left party, the Democrats of the Left, is widely respected across the political spectrum.

But in Italy’s poisonous political atmosphere, after last month’s razor-close election that narrowly ejected Silvio Berlusconi as prime minister, the selection of Mr. Napolitano still turned into a full-scale battle.

The voting stretched out over three days and could not be concluded until Wednesday, when, under the rules, a president could be chosen by a simple majority, instead of the two-thirds requirement in the initial votes.

After Mr. Napolitano won with 543 votes, 38 more than he needed, Mr. Berlusconi suggested that the new president was too close to the center-left to fulfill the traditional role of neutral political broker, and that Mr. Prodi, in his major appointments, had written the center-right out of politics.

“We are still convinced that half of the country has been excluded,” Mr. Berlusconi said in a television interview. “This is not the will of the people, but we wish him well.”

Mr. Prodi denied Mr. Berlusconi’s accusation. “Napolitano really will be the president of all Italians,” he told reporters.

The selection clears the way for Mr. Prodi to take office because one duty of the president is to form and dissolve Parliament. Mr. Napolitano is expected to be sworn in on Monday, then charge Mr. Prodi with forming a government.

But more broadly, the presidential election revealed much about the near future of Italy’s uncertain politics, and about the strategies and limitations of Mr. Prodi and Mr. Berlusconi.

While the president is often elected by a broad swath of opposing political interests, Mr. Prodi and Mr. Berlusconi could not agree.

Mr. Prodi was hemmed in by the demands of his diverse coalition of nine center-left parties, and he owed a top job to Mr. Napolitano’s Democrats of the Left, the largest party in the coalition. Given Mr. Prodi’s slim majority in the Senate, if any of the nine parties withdraws support, the coalition may collapse.

Mr. Berlusconi’s decision not to agree on Mr. Napolitano seemed to signal his calculation that Mr. Prodi’s government will in fact fall — and that Mr. Berlusconi would reap little advantage in cooperating with Mr. Prodi in any way.

“He is saying the center-left didn’t really win the elections,” said Stefano Folli, former editor of Corriere della Sera. “This position allows him to take a very strong position in opposing Prodi.”

Mr. Berlusconi reportedly has nothing personal against Mr. Napolitano, despite Mr. Berlusconi’s years of staunch oratory against Communism. Like many centrist Communists, Mr. Napolitano was in the faction that formed a party in 1989 that later became the Democrats of the Left.

Richard N. Gardner, the first American ambassador to Italy to make formal approaches to the Communist Party, in the late 1970’s, said he singled out Mr. Napolitano, then on the central committee, as his first point of contact.

“He was the one that was reputed to be the most moderate,” Mr. Gardner, ambassador from 1977 to 1981, recalled in a telephone interview. He echoed the statement of Mr. Prodi — and in fact some allies of Mr. Berlusconi — that Mr. Napolitano was capable of being a neutral arbitrator.

“That is the nature of the man,” Mr. Gardner said. “He is not going to be partial to one side or the other.”