Campaign posters plastered along the riverside in provincial capital Semarang proclaim "Jokowi Chooses Gerindra" - a reference not to the president's own political party but that of his erstwhile rival, Defence Minister Prabowo Subianto.
Jokowi officially has not endorsed anyone in the race to succeed him, but his son's status as Prabowo's running mate is widely presumed as a presidential seal of approval.
After serving the maximum two terms, Jokowi will step down this October, but with an 80% approval rating he holds huge sway over Indonesia's 205 million voters.
Prabowo, who lost to Jokowi in the last two presidential elections, holds a commanding lead this time, with analysts crediting perceived backing by the incumbent - a phenomenon some call "the Jokowi effect".
The effect is particularly pronounced in Central Java, where former Governor Ganjar Pranowo - once seen as Jokowi's natural successor - has all but lost his home advantage.
The turning point came when Prabowo added Jokowi's 36-year-old son, Gibran Rakabuming Raka, to his ticket, said Kennedy Muslim, an analyst from polling institute Indikator Politik.
"That single consequential manoeuvre has paid off handsomely in the polls for the last three months in boosting Prabowo's support," Muslim said, describing a "drastic migration of Jokowi loyalists".
It's unclear if Prabowo's double-digit lead over Ganjar and former Jakarta governor Anies Baswedan will deliver the over 50% votes needed to avoid a runoff, though recent polls put him in a strong position.
A year ago, the election frontrunner was the photogenic Ganjar – a fellow member of Jokowi's Democratic Party of Struggle (PDI-P) hoping to mirror his path from hard-working provincial chief to leader of Southeast's Asia biggest economy.
But in recent months, that picture radically altered as Jokowi appeared to shift closer to Prabowo amid reports of a rift between the president and PDI-P chairwoman Megawati Sukarnoputri.
"BLOOD THICKER THAN PARTY"
Since Prabowo controversially named Jokowi's son as his running mate in October, Ganjar's ratings in the Javanese heartland have plunged 30 points to 38% from 68%, while Prabowo's popularity has now eclipsed his.
"The sudden collapse of Ganjar's poll numbers, even in Central Java and East Java, is also because of this 'Jokowi effect'," said Muslim. "Demonstrating how powerful and consequential Jokowi's influence is...the ultimate kingmaker."
"Blood is thicker than political parties," said Sudaryono, the head of Prabowo's party in Central Java.
Agus, a 50-year-old who runs a market stall in Semarang, said: "When people see Gibran, they see Jokowi. If Gibran wasn't there, Prabowo would drop for sure."
Prabowo has undeniably run a savvy campaign, swapping former nationalistic tirades for cute dances and adopting the nickname "gemoy", meaning cute and cuddly.
At a carnival-like campaign in Tegal city, also in Central Java, complete with live music, door prizes and jumping castles, hundreds of fans in baby-blue shirts featuring Prabowo's AI-avatar braved the piercing heat to attend.
"I like his free food for school children programme," said Isnaeni, a 28-year-old mother of two, "Prabowo loves the people."
Nevertheless, Jokowi's implicit support has been crucial, said analyst Kevin O'Rourke.
"Jokowi has been a gigantic factor. Mostly it's just about him. And he has a formula that makes him popular: low inflation, social service spending and infrastructure development, and a disposition that people like," he said.
"CONVERT THE LOVE"
Observers have pointed to a worrying democratic backslide in Indonesia, but Prabowo's alleged dark past and criticism of dynastic politics appear to matter little at the grassroots, where millions identify with Jokowi's humble persona and attention to ordinary Indonesians.
When the constitutional court, at the time headed by the president's brother-in-law, changed the age eligibility rules that enabled Gibran to run for vice president, an online outcry did not trigger mass street protests.
In the past month, Jokowi has travelled to Central Java at least three times to distribute fertiliser, rice and cash assistance, raising questions about his declared neutrality.
"It's pork barrelling," said Nur Hidayat Sardini, a lecturer at Semarang's Dipenogoro University. "The social assistance has been massive."
The impact on Ganjar's campaign, lamented PDI-P's Bambang Wuryanto, has been like a "a big bomb".
The government has denied that any one candidate benefits from the social assistance programme. The president's office has not responded to questions about the neutrality complaints.
Sudaryono, from Prabowo's party, said the task was to "convert the love into votes" adding that many Indonesians were drawn to the defence minister's pledge of "continuity" of Jokowi's policies.
But analysts say such continuity is far from guaranteed.
"The vast bulk of power resides with the office of the president," said O'Rourke. "And on October 20 that will change, and Widodo will be out of power."
