ROME (AP) — Ex-Premier Matteo Renzi is challenging members of his defeated Democrats to publicly declare if they'll support the 5-Star Movement, as he tries to prevent his party from fracturing and backing its political nemesis.

Renzi took to Facebook Tuesday after national election results showed his once-dominant Democratic Party had brought the center-left to its worst showing ever, with the coalition taking less than 23 percent of the vote.

The center-right coalition had 37 percent and the anti-establishment 5-Stars 32 percent. Neither obtained enough to govern.

That outcome has kicked off weeks of horse-trading as each potential governing force tries to pick up support from elsewhere, including from disillusioned Democrats who might be tempted to back the 5-Stars.

Renzi has said the Democrats must be the opposition to any 5-Star government.