KIEV, Ukraine — After a leading contender dropped out of Ukraine’s presidential race on Saturday, the hopes of many Ukrainians and their Western supporters are now riding on a man known as the Willy Wonka of Ukraine, the billionaire owner of a chocolate candy company.

Petro Olekseyevich Poroshenko, 48, was the highest-profile Ukrainian industrialist to support the street protests that ousted President Viktor F. Yanukovych last month, and has for several weeks led in polls for the May 25 presidential election.

Known as a centrist who had previously worked for both pro-Western and pro-Russian governments, he became a strong advocate of integration with Europe after Russia banned imports of his chocolate.

On Saturday, the candidate who had been running second in polls, the former heavyweight boxing champion Vitali Klitschko, withdrew from the race, throwing his support behind Mr. Poroshenko and solidifying his lead.