The owner of the NBA's New Jersey Nets, Mikhail Prokhorov, has announced his candidacy for the presidency of Russia. His main opponent will be Vladimir Putin, the current prime minister and former president (2000-2008).

Putin has come in for some fierce criticism recently, as thousands of people gathered in public squares in Moscow, St. Petersburg, and elsewhere around the country to protest against allegations of election fraud. Putin's United Russia party lost about 20 percent of its seats in the December 4 election, but allegations put forward by independent observers say that the loss should have been much worse. Putin has so far refused comment on the subject, but President Dmitry Medvedev has promised a full investigation.

The protests were the largest seen in the country since the fall of the Soviet Union. Another set of large protests is set for December 24.

Prokhorov is a billionaire, with an estimated worth of $18 billion. He made his money in banking and metals and bought up a controlling interest in the New Jersey Nets in 2010.

Also announcing a challenge to the governmental authority was Alexei Kudrin, Putin's former finance minister, who is planning to form a new political party. Known for his conservative fiscal policies, Kudrin served as finance minister under both Putin and Medvedev. He was removed from his post recently for saying that he would not serve again under Putin.

Also certain to run against Putin in next year's presidential election is Communist chief Gennady Zyuganov, who has finished as high as second in elections past.