“The advantage to holding the decision now is that he does not have to agree to further austerity measures which will hurt his popularity further and would make it that much harder for anyone to cross the divide and vote with him,” said Nick Malkoutzis, the founder and editor of MacroPolis, the political analysis website.

But Mr. Malkoutzis and many other analysts said they believed it would still be difficult for Mr. Samaras, who is holding on to an extremely thin majority in Parliament. The prime minister nominated Stavros Dimas, a 73-year-old former member of the European Commission and fellow conservative.

Some analysts speculated that Mr. Samaras would not have made his move if he did not have the votes. Others suggested they were watching desperation.

If a new general election is held, polls suggest that Mr. Samaras’s party, New Democracy, would come in behind Syriza, though many pollsters say that there are still many undecided voters.

The head of Syriza, Alexis Tsipras, has the political advantage of having had no part in the bailout agreements that have forced the government to raise taxes, cut pensions and lay off thousands of workers. Although he has long been critical of the austerity forced on Greece by Germany and other lenders, he has worked hard to moderate his image as a radical in recent months, trying to assure investors and voters that he can be trusted with power.

But he has said repeatedly that he wants to break from austerity policies and restructure the government’s huge debt burden, which stands at 174 percent of gross domestic product.

Panos Skourletis, a spokesman for Syriza, said he did not believe Mr. Samaras would get the necessary votes. The government, he said, moved up the election so it would not have to “deal with disclosing the commitments they have toward the troika and the underpinnings of the new credit-line deal.”