BERLIN (Reuters) - Germany's conservative candidate for chancellor scrambled to boost his flagging campaign on Monday, warning voters that a left-wing coalition led by his Social Democrat rival would bring on a "severe economic crisis" after Sunday's national election.

       Armin Laschet ratcheted up his rhetoric after Olaf Scholz of the centre-left Social Democrats (SPD) won a third televised election debate https://reut.rs/3zsEEA2 on Sunday, cementing his position as frontrunner to succeed conservative Chancellor Angela Merkel.

       Acknowledging that "we are in a race to catch up", Laschet seized on Scholz's statement on Sunday that his preference is for a coalition with the Greens, and the conservative warned voters against a Scholz-led so-called Red-Red-Green https://reut.rs/3DIzZNV ruling alliance with the hard-left Linke.

       "Red-Red-Green have other ideas on economic and financial policy and they would lead Germany into a severe economic crisis if they implement them," Laschet told a news conference.

       Scholz, who serves as finance minister in Merkel's awkward "grand coalition", has repeatedly distanced himself from Linke, but has not categorically ruled out a three-way Red-Red-Green alliance, which already rules the city state of Berlin.

       At stake in the election is the future course of Europe's largest economy after 16 years of steady, centre-right leadership under Merkel. She plans to step down after Sunday's vote.

       Laschet's promise of "steadfastness" is failing to resonate with voters worried about climate change, immigration and the COVID-19 pandemic. An INSA poll for Bild on Monday put the SPD at 25% support, with the CDU/CSU conservative bloc at 22%.

       SPD co-leader Saskia Esken said Scholz had shown voters on Sunday he was a "confident, competent, likeable" candidate.

       Scholz appeared on Monday before a parliamentary finance committee to face questions over suspected failings at the government anti-money laundering agency, a unit of his ministry.

       Prosecutors raided the finance ministry this month as part of an investigation into the agency. Scholz is not accused of doing anything wrong legally.

       The timing of the raid - less than three weeks before the election - has fuelled speculation about a political motivation. Laschet said such suggestions broke a taboo about respecting the independence of the judges who ordered the raids.

       But SPD co-leader Norbert Walter-Borjans accused Laschet's conservatives of trying to exploit the investigation.

       "Because the CDU apparently has no content, it then looks at how to scandalise others," he said.

       (Writing by Paul Carrel; Editing by Tomasz Janowski and Alison Williams)