Italy’s Constitutional Court made early elections more likely on Wednesday, when it demanded changes in the electoral system that lawmakers ushered in last year.

At the behest of the center-left prime minister, Matteo Renzi, the lower of house of parliament introduced a two-round system to elect its members, which would make it easier for any one party, or coalition of parties, to win a majority.

But voters rejected an overhaul of the Senate that was meant to work in tandem with the lower-house reforms in a referendum last month.

Renzi’s plan was to reduce the upper chamber to a relatively toothless body of regional deputies.

Now the two chambers remain equally powerful, but they would be elected under different rules — increasing, rather than decreasing, the risk of divided government.

Five Star menace

Wednesday’s ruling means lawmakers must harmonize the electoral laws, which will probably mean a switch back to a system of proportional representation in the lower chamber.

That, in turn, would lessen the chance of a Five Star victory.

The anti-establishment movement’s ambiguous views on NATO and Russia as well as its hostility to the German-led currency union in Europe worry mainstream leaders in Brussels and Rome.

The Five Stars have nevertheless polled neck and neck with Renzi’s Democrats since the middle of last year.

Splintered

The right is splintered. Former prime minister Silvio Berlusconi’s Forza Italia and the anti-immigrant Lega Nord would each get around 12-13 percent support.

Nuovo Centrodestra, which rules in coalition with the center-left, could lose all its seats.