The MCG, a party only created eight years ago that previously failed to win a cabinet seat, elected lawyer and national MP Mauro Poggia to the seven-person government.
Pierre Maudet and François Longchamp of the centre-right Liberals (PLR) topped the polls as they won-re-election, while the Christian Democrats also elected two representatives, newcomers Serge Dal Busco, mayor of Bernex, a local municipality, and Luc Barthassat, a national MP.
Green candidate Antonio Hodgers, another national MP, joined the government and Anne Emery-Torracinta, a cantonal parliament MP, was the sole Social Democrat — and only woman —to win election.
The latest round of voting comes a month after a first round when voters also chose a new parliament divided roughly into three power blocs representing the left, centre-right and right wing.
Michèle Künzler, Green party incumbent cabinet minister, was knocked out of the running in the first round, while another incumbent, Isabel Rochat, of the PLR, was eliminated in the second round.
Other incumbents, Charles Beer (Social Democrats), David Hiler (Greens) and Pierre-François Unger (Christian Democrats) decided not to seek re-election, so Sunday’s result brings five new faces to Geneva’s government.
The MCG has developed a reputation as an anti-foreigner party, campaigning in 2009 under a banner for “Geneva and Genevans first”.
But Poggia appears more open to compromise than his controversial running mate, Eric Stauffer, who came last in the election, the ATS news agency reported.
Pierre Ruetschi, editor-in-chief of the Tribune de Genève, said it remains to be seen whether the MCG, with its reputation for “troublemaking” will make demands on Poggia in government, or whether he will act more collegially.
“It’s a great joy for me and the MCG,” Poggia told media after learning of his election.
“We are beneficiaries of a hope for change for Geneva,” he said.
“I hope we can be worthy of this,” Poggia said.
The election campaign revolved around concerns over Geneva’s economic future, an ongoing housing crisis and law and order issues.