By James Mackenzie
ROME (Reuters) - Italy's anti-establishment 5-Star Movement chose a television journalist as its candidate for president on Tuesday and hinted it could co-operate with center left if she were elected.
Choosing a successor to President Giorgio Napolitano, whose term ends on May 15, is a vital step toward resolving the stalemate created by an inconclusive general election in February that left no party able to form a government.
Once elected by parliament, the new president's first task will be to find a way out of the deadlock, either by persuading the parties to come to an accord or by calling new elections.
The two houses of parliament, along with delegates from the regions, will start voting on Thursday, a process that may involve several rounds. No clear favorite has emerged among the divided parties.
The 5-Star Movement's leader said if Pier Luigi Bersani's center-left bloc - which won the most seats in February but not enough to govern - agreed to back investigative journalist Milena Gabanelli for president, 5-Star may re-consider its refusal to have anything to do with it.
"I'd like to give Bersani a piece of advice, without any irony or joking. Seriously, it could be a meeting point. Vote for Gabanelli," Beppe Grillo said in online message. "It would be a great signal."
Bersani has repeatedly called on 5-Star to form a government with him, but his overtures have been constantly rejected by Grillo, whose following is based on public disgust with mainstream politicians.
Grillo did not explicitly say he would consider forming a coalition with Bersani, but spoke of co-operation in a way he has declined to in the past.
"Think about it, it could really be the beginning of who knows what, a collaboration, it could be. Try it, try it and we'll see," he wrote.
Gabanelli, a well-respected journalist from state broadcaster RAI, is a complete political outsider and Bersani and his Democratic Party may prefer a more establishment figure for the post which is supposed to embody national unity.
Having made hard-hitting programs often targeting political corruption, Gabanelli's candidature would infuriate Silvio Berlusconi, the scandal-plagued center-right leader with whom Bersani has been trying to do a deal over the presidency.
There had been speculation that 5-Star could back former Prime Minister Romano Prodi, who is also strongly opposed by Berlusconi but is supported by elements of the center-left.
But in the movement's online consultation of its members Prodi came only eighth on a short-list of 10 candidates.
The former president of the European Commission is among the names most frequently mooted in the media as a possible president but Berlusconi has rejected supporting one of his oldest political rivals as head of state.
The other name most often spoken of is former Prime Minister Giuliano Amato, who is well-known outside Italy for his handling of a financial crisis in 1992 but is handicapped by his image as a member of the traditional political elite, now widely distrusted in Italy.
As well as a ceremonial function, the head of state has an important, broadly defined political role in overseeing government, a function Napolitano had to carry out during the 2011 financial crisis when he appointed Mario Monti to lead a technocrat administration.
Grillo was prevented from standing because a manslaughter conviction following a traffic accident in 1981 makes him ineligible under his own party rules.
(Additional reporting by Gavin Jones; Editing by Robin Pomeroy)