ROME — When Matteo Renzi burst onto Italy's national political stage, he set out to consign all that was outdated and ineffective in the country to the scrap heap, pledging to make economically lumbering Italy more competitive.

Now, not even three years into office as prime minister, Renzi himself risks being trashed.

Much to his alarm, a yes-or-no referendum Sunday on government-championed constitutional reforms has been transformed by rivals into a virtual plebiscite on the 41-year-old leader, Italy's youngest.

A win by the “No” camp on a centerpiece reform of his government would be expected to trigger Renzi's resignation.

Some political opponents are also depicting Italy's referendum as an occasion to pass judgment on the country's ruling elite. They hope to tap into the populist fervor bubbling up across much of Europe — and even across the Atlantic, with the U.S. presidential victory by political outsider Donald Trump.

“Go with your gut. Look them in the face and vote ‘No,'?” comic Beppe Grillo exhorted several thousand followers of his anti-establishment 5-Star Movement after a march near Rome's ancient Mouth-of-Truth monument.

“Don't do what Beppe Grillo said,” Renzi countered a few days later. “Grillo said vote not with your brain, but with your gut. That's absurd. I say, ‘Vote with your brain. The future of your children depends on it.'?”

One of the constitutional reforms would reduce the Senate from 315 to 100 members and strip them of most of their powers, including holding crucial no-confidence votes.

The senators would also no longer be elected by voters. With Parliament's current two legislative chambers now required to give not one but two rounds of approval to every bill, Renzi contends the Senate overhaul will accelerate law-making.

Another reform would give some powers now held by the regions to the central government. “Yes” backers say that will reduce the frequent, drawn-out court battles between Rome and Italy's regional governments.

“No” advocates, which include the 5-Star Movement, some former Communists in Renzi's Democratic Party and the anti-immigrant regional Northern League party, argue the measures would erode democracy by strengthening the executive branch too much.

That argument is sensitive in a country whose 1948 Constitution was forged after World War II and the disastrous fascist dictatorship of Benito Mussolini.

Constitutional law expert Gino Scaccia said he worries that voters won't examine the reforms' merits but instead will “vote based on their position in favor or against the government.”

Under the constitution, a referendum on changing it can be held under various circumstances. One of them is if at least one-fifth of the lawmakers in one of Parliament's chambers ask for it. That happened in this case, with the 5-Star Movement among the opposition forces spearheading the successful petition for a popular referendum on Renzi's reforms.

Self-assured often to the verge of cockiness, Renzi had promised to resign if voters reject the reforms. But after polls indicated that defeat was likely, Renzi has been on the stump to persuade voters that the ballot is not about him.

“Is it written ‘obnoxious Renzi' or ‘let's change this country' on the ballot?” the premier asked on a TV show.

Perhaps Renzi's proudest achievement has been a law making it easier to fire workers, in hopes that Italian employers will hire more whenever the economy picks up. But so far Italy's economy has resisted efforts to grow again.

Analysts suggest that a referendum defeat, or even Renzi's resignation, won't rattle the markets or the European Union. Italy's oft-bickering coalition governments have frequently collapsed far short of Parliament's five-year term.