JAKARTA (REUTERS) - Already favourite to become Indonesia's next president, Jakarta governor Joko Widodo's popularity has surged since his candidacy for the July election was announced last month, according to the latest opinion polls.

Known locally as Jokowi, the Jakarta governor is widely regarded as a shoo-in for top job in the world's third-largest democracy.

Support for Jokowi leapt to 45 per cent after his party named him as its candidate, from 35 per cent before, according to a survey released Wednesday by Roy Morgan International.

The survey showed support for rival Prabowo Subianto, a former general, holding at 15 per cent, while tycoon Aburizal Bakrie trailed with 11 per cent.

The "Jokowi factor" has also boosted ratings for his party, the opposition Indonesian Democratic Party (PDI-P) led by former president Megawati Sukarnoputri, as it campaigns for a parliamentary poll due on April 9.

By nominating Jokowi, Megawati appeared to set aside her own ambitions in order to improve her party's chances of returning to power.

"As soon as his candidacy for the presidential race was announced, PDI-P's fortunes jumped from 27 to 37 per cent," wrote Debnath Guharoy of Roy Morgan International.

"The long race looks like it is well and truly over, even before it's begun."

Another survey released this week by the Center for Strategic and International Studies showed support for both Bakrie's Golkar and Prabowo's Gerindra parties dwindling to less than 20 per cent.

Only parties that garner at least 25 per cent of the national vote or 20 percent of seats in parliament can field candidates for the presidential election three months later.

In little over a year since becoming Jakarta's governor, Jokowi has earned a reputation for clean and effective governance.

Ordinary Indonesians, used to a sleepy bureacracy run by an entrenched and often corrupt elite, like the common touch Jokowi demonstrates with his almost daily visits to low-income neighbourhoods in the capital.