JAKARTA, Indonesia — Indonesia’s president, Joko Widodo, preparing for his second term, faces a sudden loss of public support amid mounting crises, including student protests, burning forests and deadly violence in distant Papua province.

Mr. Joko won re-election handily in April, defeating his main rival by 11 percentage points. But even before his scheduled inauguration next month, his handling of a controversial corruption bill threatens to undermine his second-term agenda.

The president’s popular support began falling, political analysts said, when he approved passage of legislation this month to strip the respected Corruption Eradication Commission of key powers, including the authority to wiretap public officials suspected of wrongdoing.

Student protesters have called on Mr. Joko to revoke the measure and restore the commission’s power by issuing an emergency decree, but he said on Monday that he would not.