FILE PHOTO: German conservative Friedrich Merz speaks about his candidacy to succeed Chancellor Angela Merkel as leader of the Christian Democrats, in Berlin, Germany October 31, 2018. REUTERS/Hannibal Hanschke/File Photo

BERLIN (Reuters) - The pro-business economic liberal Friedrich Merz is the most popular among voters of the three candidates vying to succeed Chancellor Angela Merkel as leader of Germany’s Christian Democrats (CDU), a poll showed on Thursday.

Merkel triggered the race to succeed her when the 13-year chancellor announced she was resigning her party office and preparing a gradual exit from politics after her conservatives suffered setbacks in two key regional elections last month.

With the race still in its very early stages, a YouGov poll for business daily Handelsblatt showed 23 percent of the public favoring Merz, an old rival whom Merkel defeated in an inner party battle almost two decades ago during her rise to the top.

With a month to go until a party congress chooses the new leader, 17 percent of those polled backed current CDU general-secretary Annegret Kramp-Karrenbauer, dubbed “mini-Merkel” because of their political closeness to the chancellor.

A third candidate, Health Minister Jens Spahn, best known for his calls for tougher immigration controls, had the backing of 7 percent of the voters.

Though Merkel says she plans to stay in office until 2021, the party’s new leader would be a leading candidate to succeed her, although only the centrist Kramp-Karrenbauer could easily continue the existing coalition with the Social Democrats.

More than a third of respondents had no view either way, suggesting that the picture could change radically in a race in which further candidates could yet emerge.