ROME — Its poll numbers are plummeting. Its members of Parliament are defecting. Its leaders complain about back-stabbing while supporters flee to the left and the right.

And it runs the Italian government.

Italy’s Five Star Movement, the anti-establishment party born on the internet that was supposed to revolutionize Italian politics, increasingly looks to be on the verge of cratering, only two years after winning the largest vote in national elections.

With Italy’s economy essentially stuck and its power waning, there is rising clamor that the party’s dysfunction and identity crisis may not just bring down the government but drag Italy down with it.

Five Star is not likely to collapse tomorrow. But its new governing coalition with the establishment, center-left Democratic Party, which was supposed to put Italy on track after Five Star’s rocky divorce from Matteo Salvini’s hard-right League party this summer, is already clearly deeply troubled and has done little more than extend Italy’s malaise.