Incumbent Yudhoyono, 59, one of the former Suharto-era generals with a cleaner reputation, will be competing for a second five-year term against former president Megawati Sukarnoputri and current Vice President Jusuf Kalla.

Widely known by his initials SBY, Yudhoyono is hoping to win a clear majority to avoid a September runoff. A candidate is required to win more than 50 percent of the votes and at least 20 percent of the vote in half of the country's 33 provinces to win without a second-round vote.

In the April legislative election, Yudhoyono's ruling Democratic Party garnered 20 percent of vote - up from seven percent in 2004 - to become the largest party in Parliament.