Greece's next government may hold a $510 billion trump card if it heeds voters' demands to renegotiate bailout agreements with the European Union.

The nation owes about €395 billion ($510 billion) to private bondholders, public bodies such as the International Monetary Fund and European Central Bank and other creditors, according to data compiled by Bloomberg. About €252 billion of that is due to official organizations that used their status to avoid the losses suffered by ordinary bondholders when Greece restructured its debt two months ago.

Greek voters are demanding their leaders renegotiate the terms of rescue packages that have imposed unprecedented austerity on the country since 2010. One potential prime minister, Syriza party leader Alexis Tsipras, has pledged to tear up the EU-led bailout agreement. With Greece owing a sum roughly equal to Switzerland's economy, the fallout for taxpayers could be calamitous if the country walks away.