MADRID (Reuters) - Spanish newcomer party Ciudadanos would come a close second to the ruling People's Party, and would probably be the main kingmaker, if a national election due in December was held now, an opinion poll showed on Sunday.
Ciudadanos, a market-friendly party founded nearly a decade ago in the northeastern region of Catalonia but which expanded nationally only earlier this year, has been steadily gaining support over recent months on a message of moderate change.
Backing for the party has jumped to 22.5 percent, the Metroscopia survey released by El Pais newspaper showed, putting it ahead of the main opposition socialists and leftist Podemos.
That compares with 16.1 percent before September, when it made big headway in regional elections in Catalonia to become the second biggest group in the assembly there.
The center-right People's Party of Mariano Rajoy is still seen as likely to win the Dec. 20 election, with 23.5 percent of the vote, stable from last month, while the socialists (PSOE) would fall to 21 percent and Podemos would rebound slightly to 17 percent.
The poll was carried out from Oct. 26-28, just as Catalan separatists launched their roadmap for independence, which Rajoy has vowed to block because the Spanish constitution does not allow for a region to break away.
Rajoy held talks with the socialist party, Ciudadanos and Podemos earlier this week to gather political support against the secessionist drive.
All four parties want Catalonia to stay in Spain, although Podemos has said it would support a referendum on the matter.
The Metroscopia poll, which for the first time projected the number of seats each party would get in the national parliament, showed Ciudadanos would be able to back both a PP- and a socialist-led government and secure a stable majority for each.
The Ciudadanos leader, Albert Rivera, was also rated the country's best-regarded politician by a wide margin.
Opinion polls have been highly volatile in recent months as a majority of voters turn their backs on the traditionally dominant PP and PSOE, tainted by corruption and seen as responsible for the worst economic crisis in decades.
A more comprehensive quarterly opinion poll from the Sociological Research Center, deemed the most reliable in the country, is due to be released next week.
Reporting by Julien Toyer; Editing by Andrew Bolton and John Stonestreet