BELGRADE, Serbia (AP) — Serbia’s youth movement scored a stunning election victory against the country’s longtime strongman Aleksandar Vucic. But turning its promises of sweeping democratic reforms into reality could prove far more difficult.

The diverse, leaderless movement, whose candidates have little political experience, has promised to root out corruption, free the media and restore the rule of law after Vucic’s 14 years in power.

Though armed with a strong mandate for change stemming from a convincing election victory, a new government will still encounter a myriad of hurdles along the way.…