ROME—In 2014, 39-year-old
electrified Italy’s voters, sweeping to power on promises to “demolish” the country’s discredited political establishment and revive an economy still badly bruised from the sovereign-debt crisis.
Now, more than a year after he was forced to resign as prime minister, polls show Mr. Renzi’s popularity plummeting, frustrating hopes of a comeback for a young politician some hailed as the reformer Italy badly needs. His sinking fortunes and those of his center-left Democratic Party, Italy’s largest mainstream and currently ruling party, increase the chances that March 4 parliamentary elections will produce a hung parliament, undermining the prospect of a strong, stable government capable of rebooting Italy’s troubled economy.
When Mr. Renzi, a brash Tuscan and former mayor of…