Greece and the euro: What's next?

NEW YORK (CNNMoney) -- Investors are getting increasingly worried about whether Greece will remain in the eurozone. And they should.

There are a series of upcoming events that could spell the end of a deal, put in place nearly three months ago, to restructure Greece's debt under strict terms dictated by the European Union, International Monetary Fund and European Central Bank, known as the troika.

"The threat from Greece remains real, and Greece exiting the euro area would likely have contagion effects that cannot easily be addressed in the current set-up," said Bank of America Merrill Lynch analysts in a note Monday. "The next weeks are crucial."

Greece has been struggling under a mountain of debt, as it tries to push through unpopular austerity measures and get its economy on solid footing. Without a cohesive government, that battle just got tougher.

Here's what next in the Greek political drama, and what it could mean for the rest of Europe and the global economy.

Where do things stand after last week's national elections? There is still no party that has been able to form a new government. The two parties from the previous ruling coalition that supported austerity and the debt deal, New Democracy and Pasok, only have 149 seats between them and 151 are needed.

So far, none of the other parties are willing to join them, given Greek voters' anger over the harsh austerity measures.

If Greek President Karolos Papoulias is not able to bring together a new ruling coalition by Thursday, he is expected to call for another round of voting, likely in mid-June.

What is likely to happen if new elections are held in June? Recent polls and various experts seem to agree that the Coalition of the Radical Left, also known as Syriza, would be the top vote getter in the next round. Syriza has gained solid support since finishing second in last week's round of voting.

If it can form a majority coalition with other anti-austerity parties, that would leave Greece with a government opposed to the earlier deals made with the EU, IMF and ECB, which has to approve funds for Greece that would allow the government to pay its bills and make its bond payments.

Whether the June election result would lead to a disorderly default and a Greek exit from the euro is far less clear.

"Even Syriza is not really interested in getting out of the euro. Their primary focus is to renegotiate the bailout package," said Dimitri Papadimitriou, economics professor and expert on Greece from Bard College.

But without financial support from the so-called troika, it will be tough for Greece to meet its financial obligations.

Can Greece stop paying its bills and still stay in the eurozone? That is the biggest unknown, and probably the biggest worry for markets.

Elisabeth Afseth, fixed income analyst for Investec Bank in London, said if Greece stops paying its bills, that will mean the end of the funding it so desperately needs. If that happens, it won't have much choice but to start issuing its own currency to pay its ongoing bills.

But Papadimitriou said that other European leaders are also loath to have Greece exit the euro, due to the shock it might cause for the continent's already-fragile financial system. Therefore, he said, it is possible, albeit unlikely, that there could be yet another new deal even if Greece stops paying what it owes.

"I would expect the European finance ministers' meeting to have intense discussions this week," he said. "The best case for keeping Greece within the euro would be for the rest of Europe to be proactive in trying to come up with a renegotiated deal suitable for all parties. But I'm not optimistic."

What's the best case scenario for Greece leaving the euro? In the best case, the ECB steps in and contains the so-called contagion effect.

While the central bank's drumbeat has been to not be the lender of last resort, it has also made it clear that it would do everything in its power to keep the crisis from spreading.

A dozen European countries are already in recession but thanks to Germany's surprise growht, the entire EU and eurozone managed to stave off recession in the first quarter.

Even in this best case scenario, one in which measures to prop up the non-Greek sovereign debt work, the austerity measures needed to pay for them would send the remaining countries of the eurozone and EU into an even deeper, more prolonged downturn.

Yields could soar on government debt for Portugal and Ireland, let alone much larger economies like Spain and Italy, vastly increasing the costs for the remaining European governments that are paying for various bailouts.

That would also weigh on the already slowing growth in both the United States and Asia.

How bad could things get? Things could be worse than that -- far worse.

"I don't think anyone at the present time can quantify the contagion effect of a disorderly exit of Greece from the eurozone," said Papadimitriou. "No one can predict the markets. They have a mind of their own.

In a worst-case scenario, the Greek exit prompts other countries to leave the euro, as voters there follow Greek voters' lead and rebel against austerity measures.

"As it stands now, there's no precedence for leaving," said Afseth. "If Greece leaves, all of sudden there is precedent."

If larger countries follow Greece out of eurozone, it could cause a meltdown in the European banking sector, which holds billions of euros of sovereign debt of the other troubled economies, as well as private sector loans to consumers.

In turn, businesses in those countries would be unable to pay given their suddenly devalued currency.

While U.S. authorities have said U.S. banks have relatively limited exposure to European sovereign debt, the major banks here do have exposure to the European banking system, so a meltdown in European markets would be felt in the United States and around the globe.