"If I happen to come across any false information about me, I will deny it," Vice-President Jusuf Kalla declared after opening a World Press Freedom Day event in Jakarta on Wednesday.

Indonesia's elder statesman seemed to be responding to recent rumours that he was a key figure in an emerging power struggle within Golkar, Indonesia's second-largest political party.

There was also a remark by senior lawmaker Zulkifli Hasan on Tuesday that Mr Kalla played a key role in former minister Anies Baswedan running for Jakarta governor against the incumbent Basuki Tjahaja Purnama, who is a close ally of President Joko Widodo.

Mr Kalla's spokesman, Mr Husain Abdullah, yesterday told CNN Indonesia that it was not a secret that the Vice-President had suggested that Gerindra Party chief Prabowo Subianto field Mr Anies for the Jakarta elections - but he denied any friction between Mr Kalla and the President.

Political insiders, however, say the statements hint at a growing rift between Mr Joko and his No. 2.

These cracks at the highest echelon of the Istana, whether implied or explicit, have added to the mounting pressure on Mr Joko as he continues to push through reforms, which will require the support of Golkar.

The party helped tip the balance of power to President Joko after it joined the ruling coalition last year.

But with current Golkar chief Setya Novanto being investigated for graft, there has been talk that certain factions within the party are preparing a candidate to be the next chief, with Mr Kalla possibly playing kingmaker.

One possible candidate is Ms Siti Hediati Hariyadi, a daughter of former president Suharto, Golkar's founder.

It was Golkar's move to join the ruling coalition last year that gave the President majority support in Parliament for the first time since he was elected in late 2014. One of those policy victories was the Tax Amnesty Bill, which was passed with Golkar's help last year and successfully implemented to beef up Indonesia's tax coffers.

If Mr Joko, or Jokowi as he is called, loses Golkar's support, which will likely happen if Mr Setya is ousted - with or without any intervention from Mr Kalla - the ruling coalition will lose its 62 per cent control of the House, leading to a shift of power away from the Istana.

This will undoubtedly make it harder for Mr Joko to introduce new policies or enact new laws designed to take Indonesia forward.

"Any leadership change in Golkar could provide a challenge to Jokowi because under Setya, Golkar declared that it will support Jokowi's re-election in 2019," Professor Hamdi Muluk, who teaches political psychology at the University of Indonesia, said yesterday.

Mr Kalla's support for Mr Anies at the gubernatorial election would be taken as a personal affront by the President, said observers.

This is because Mr Prabowo was Mr Joko's rival in the 2014 presidential election, while Mr Anies was sacked as culture and education minister just two months before he announced his candidacy with Gerindra last year.

That Basuki, better known by his Chinese nickname Ahok, had lost so badly at the April 19 polls to Mr Anies, has surely raised the stakes for the race to Istana in 2019.

Mr Joko has thus far kept his cards close to his chest, and has not reacted to Basuki's loss or speculation of a power play involving his own Vice-President. But such undercurrents, or arus bawah in local jargon, cannot be ignored if he wants to be re-elected, said observers.

Many said the President will begin consolidating his power, starting with an upcoming leadership reshuffle, in a bid to gain new allies as he prepares for the 2019 election. He is expected to face Mr Prabowo, who has indicated that he will run again for the presidency.

Experts such as Prof Hamdi said Mr Joko will need to prove that he remains in control of his government and ensure that it functions effectively.

He added: "Politicking will always happen and the winds of change will get stronger approaching 2019, but we hope (Mr Joko and Mr Kalla) will continue to work together regardless of their differences in the Jakarta gubernatorial election. It is not good if the President and Vice- President are engaged in rivalry."