More than 100 million people are voting on Wednesday in one of the biggest elections in the world. The contest for the top prize — the presidency of Indonesia — is a three-way race.

But looming large is someone not on the ballot.

That person is Joko Widodo, the incumbent president, who is not allowed to seek a third five-year term and will step down in October. A decade after Mr. Joko presented himself as a down-to-earth reformer and won office, he remains incredibly popular.

Many of his supporters say that he has largely delivered on his promise of putting Indonesia on the path to becoming a rich country in the coming decades, with ambitious infrastructure and welfare projects like the plan to build a new capital city and a universal health system.

At the same time, Mr. Joko has also overseen what critics describe as the regression of civil liberties. He has stripped down the powers of an anti-corruption agency, rammed through a contentious labor law and, more recently, appeared to engineer the placement of one of his sons on the ballot for vice president.

Making matters worse, critics say, is the presidential hopeful he appears to be backing: Prabowo Subianto, a former general who was once a rival of Mr. Joko and who is accused of committing human rights abuses when Indonesia was a dictatorship. Mr. Prabowo, whose running mate is Mr. Joko’s son Gibran Rakabuming Raka, has been ahead in the polls.