Indonesian presidential front-runner Joko "Jokowi" Widodo on Monday named popular former Vice President Jusuf Kalla as his running mate in July's election, boosting his chances of becoming the next leader of the world's third-largest democracy.

Opinion polls show a pairing of Jokowi from the main opposition party, PDI-P, and Kalla from the second-biggest party, Golkar, has a significant lead over the main rival. If no ticket wins more than 50 percent of the vote in the July 9 election, there will be a second round held in September.

Jokowi and Kalla are up against Prabowo Subianto, a former general with a checkered human rights record, and his running mate, Hatta Rajasa, a former chief economic minister.

Kalla is seen as bringing strong business credentials to the ticket. Jokowi has enjoyed a meteoric rise on the political scene since becoming the governor of Jakarta in late 2012.