Voters in the wealthy northern Italian regions of Lombardy and Veneto are heading to the polls to decide if they want to seek greater autonomy from Rome, riding a tide of self-determination that is sweeping global politics.

While the twin referendums on Sunday are non-binding, a resounding "yes" vote would give the presidents of the neighboring regions more leverage in negotiations to seek a greater share of tax revenue and to grab responsibility from Rome. The leaders want more powers in areas such as security, migration, education and the environment.

Lombard President Roberto Maroni has lowered expectations, saying he would be happy with a 34 percent turnout among the region's 7.5 million voters, equal to the national turnout in a 2001 constitutional referendum.

The Veneto autonomy drive dies if voter turnout is below 50 percent plus one of the region's 3.5 million voters.

Even though the referendums — which are approved by Italy's constitutional court — don't seek independence, the autonomy drive is a powerful threat to Rome's authority. Together, Veneto and Lombardy account for 30 percent of GDP and nearly one-quarter of the nation's electorate.

Both regions are run by the anti-migrant, anti-Europe Northern League, which has long given up its founding goal of secession as it seeks a national profile. Also supporting the referendum is former Premier Silvio Berlusconi's Forza Italia and the populist 5-Star Movement.

With the Democratic Party urging its voters to abstain, the votes Sunday will measure the mood ahead of a national election next year, when Berlusconi says he will make autonomy a goal for all of Italy's regions.

Critics of the referendum argue that the non-binding vote carries no legal weight, is not needed to trigger autonomy negotiations and is a costly waste of resources.

Yet such arguments play into the hands of the "yes" campaigners, who see such put-downs as part of an anti-democratic, elite, centrist decision-making in Rome. Those sentiments have been echoed in the Catalan independence drive in Spain, in the U.S. election of Donald Trump as president and in Britain's vote to leave the 28-nation European Union.

The Italian constitution already grants varying levels of autonomy to five regions in recognition of their special status: the largely German-speaking Trentino-Alto Adige; the French-speaking Aosta; the islands of Sardinia and Sicily; and the region of Friuli-Venezia Giulia for its position on the border with then-Yugoslavia as a Cold War hedge.

Veneto was twice denied by the constitutional court to chance to hold a referendum for autonomy before a 2001 constitutional change that allowed Italy's 15 regions to seek autonomy.

These votes Sunday are the first referendums to pose the question to voters, while Emilia Romagna, a center-left region, has recently opened talks with Rome on greater autonomy without a popular vote.