With virus cases rising and the vaccination drive delayed, the campaign opened Sunday for regional elections in the Spanish capital that are likely to cement the right-wing's hold on the country's wealthiest region.

If latest polls are correct, the May 4 election would hand victory to the region's right-wing leader Isabel Diaz Ayuso, whose Popular Party (PP) might have to govern with support of the far-right Vox.

The vote could have important ramifications for national politics and particularly for the political future of some leaders, but analysts say it's unlikely to immediately affect the left-wing coalition of Socialist Prime Minister Pedro Sanchez.

He has become personally involved however, and told a rally Sunday that voters had a choice between "the path of a (economic) rebound" with his party or a government of "social exclusion, the far-right, and corruption" with the PP and Vox.

Sunday marked the start of a two-week campaign that ends on May 2, two days before a snap election Ayuso called on March 10 after she broke off her coalition agreement with the centre-right Ciudadanos party.

If polls are correct, the May 4 vote looks set to hand victory to the region's right-wing leader Isabel Diaz Ayuso
If polls are correct, the May 4 vote looks set to hand victory to the region's right-wing leader Isabel Diaz Ayuso COMUNIDAD DE MADRID / Handout

At stake is the "jewel in the crown" -- leadership of Spain's richest region, with a population of 6.6 million that has also suffered the country's worst coronavirus toll.

Six parties are contesting the vote: the PP, the Socialists and the far-left Podemos -- partners in Spain's minority ruling coalition -- Ciudadanos, Vox and the hard-left Mas Madrid, with surveys consistently putting Ayuso in front.

Most polls suggest the 42-year-old will secure around 40 percent of the vote, with a survey published Friday giving her 56-57 deputies in the 136-seat regional assembly, while falling short of the 69 needed for an absolute majority.

Seats are attributed on a proportional basis, but a party needs five percent of the ballots to have seats.

With Ciudadanos not assured of reaching this threshold, the PP's natural bedfellow would be Vox, tipped to win 13-14 seats, with a tie-up likely securing a majority.

"Polls suggest the right-wing bloc would get approximately 52-53 percent of the vote, but there could be last-minute shifts that could end up tipping the balance," Pablo Simon, a political scientist at Madrid's Carlos III University, told AFP.

Spanish hard-left Podemos party leader Pablo Iglesias dropped a political bombshell, saying he would resign as deputy prime minister to run in the Madrid election
Spanish hard-left Podemos party leader Pablo Iglesias dropped a political bombshell, saying he would resign as deputy prime minister to run in the Madrid election AFP / PIERRE-PHILIPPE MARCOU

"A very likely option is that the PP will govern alone (in a minority) with Vox's parliamentary support, but without them holding public office."

The vote comes at a tricky time for Ayuso as infections keep rising in Madrid, which has a 14-day incidence rate of around 350 cases per 100,000 inhabitants, compared with a national average around 200, and which accounts for 20 percent of Spain's 76,900 deaths.

Known for her fierce opposition to the Sanchez government, Ayuso called the election in an apparent bid to shore up political capital she has earned through resisting pressure to impose tighter virus restrictions on the local economy.

Just days after Ayuso's election call, Podemos leader Pablo Iglesias dropped his own political bombshell, saying he would resign as deputy prime minister to run in the election.

From the start, Ayuso, a rising star within the PP, has framed the May 4 polls as a choice "between Communism or freedom" and tried to give the election national overtones, helped by Sanchez' personal involvement in the campaign and Iglesias' decision to run.

She told a rally Sunday: "He is the candidate in Madrid" in reference to Sanchez and the Socialists.

All six candidates will take part in a live televised election debate on April 21.

In the last election two years ago, the PP suffered its worst defeat in decades, but Ayuso was handed a lifeline when the Socialists were unable to form a coalition.

Simon felt the outcome in May was unlikely to have an impact on Sanchez's coalition.

"If the PP gets a really good result, it will rise in the polls and obviously... it won't be in (Sanchez's) interest to break up the government or call elections," he said.