Update, 12:30 p.m.: Papandreou has dropped the referendum, but the confidence vote will go ahead as planned tomorrow.

The Greek government is teetering on the brink of collapse following Prime Minister George Papandreou’s surprise announcement of plans for a referendum on a euro zone bailout.

Greek Prime Minister George Papandreou speaks with the media as he leaves a G20 summit in Cannes, France Wednesday. (Markus Schreiber/AP)

Finance minister Evangelos Venizelos has condemned Papandreou for asking that the European bailout package be presented to Greek voters for approval, saying that the use of the euro “cannot depend on a referendum.” Several members of the ruling Socialist party, Pasok, have defected and after calling an emergency meeting, Papandreou may be backing away from the referendum altogether.

The beleaguered prime minister is trying to hang on, but it is still believed he may step down as party leader and prime minister. If Papandreou falls, who will follow? The Wall Street Journal suggests the following scenarios:

1. Another Socialist minister steps in, likely Venizelos, and holds the role for a short time until an election could be held. Likelihood: Possible.

2. A member of the party suggests a government of national unity is formed, also a short-term solution until elections could be held. Likelihood: High.

3. Papandreou calls for snap elections, which could be held as soon as three weeks after they are called. Likelihood: Low.

4. The prime minister could stay, despite the possibility of his surviving a confidence vote Friday being low. Likelihood: Low.

Papandreou, who has been prime minister of Greece since 2009, comes from a long line of powerful men — both his father and grandfather served as the country’s prime minister. Papandreou previously served as Minister for National Education and Religious Affairs and Minister of Foreign Affairs.

Upon election, Papandreou took over a country with budget deficit of 12.7 percent of GDP, four times the eurozone’s limit, a debt of $410 million, and an unemployment rate of 10 percent.

Papandreou has favored austerity measures as a response to the country’s struggling economy, an unpopular move that has resulted in crippling nationwide strikes and protests that at times turned violent.

He narrowly survived a confidence vote once before, in June.

Read more on Greece’s crisis from the Washington Post:

World: Greek lawmakers break with Papandreou over bailout referendum

Business: Greek crisis, other global financial woes crash the G-20 party in Cannes

World: On Greek debt, lessons from South America

Business: European Central Bank cuts rates