By Francois Murphy

VIENNA (Reuters) -Former Austrian Chancellor Sebastian Kurz's trial for perjury enters its last day on Friday and a verdict is due that could kill any chance he has of returning to politics. A potentially far more menacing case for Kurz still looms.

WHO IS SEBASTIAN KURZ?

Kurz became one of the youngest leaders in the world in 2017 when, aged 31, he formed a coalition with the far-right Freedom Party (FPO). That coalition collapsed amid scandal in 2019 when the FPO's then-leader was embroiled in a video sting. Kurz then won a snap election and formed a coalition with the Greens.

Kurz became a star among European conservatives, particularly in Germany, for his youth, slick communication and hard line on immigration similar to the FPO's. Critics say he put power and political gain before principle.

The left-wing Greens forced him from office in 2021 after prosecutors placed him under investigation on suspicion of corruption. Kurz, who then quit politics, denies any wrongdoing. The conservative-Greens coalition he formed remains in power.

Austria's ruling conservatives have slid in polls since Kurz left office and are likely to lose seats in a parliamentary election this year. That has prompted speculation, particularly among supporters, that he could eventually lead them again.

Kurz says he is happy in his new career as a businessman. While some in his party still want him to return, polls show a large majority of Austrians do not.

Any criminal conviction would be a serious blow to a potential political comeback.

WHAT IS THIS PERJURY CASE ABOUT?

In 2020, Kurz testified under oath at a parliamentary commission investigating allegations of corruption stemming from the sting video.

He was asked about his involvement in picking executives for a newly-formed state holding company, OBAG, which was formally his finance minister's responsibility.

Kurz said he was "involved in the sense of informed" but did not play an active role in appointments. Prosecutors say Kurz was in fact calling the shots himself.

Their evidence includes text message exchanges, including between Kurz and Thomas Schmid, an erstwhile ally and senior finance ministry official, who became head of OBAG under Kurz.

Schmid has now turned state witness, though has yet to secure immunity.

Lawyers for Kurz have depicted Schmid as unreliable because, in order to obtain an immunity deal, he must produce evidence that proves vital, which they argue has pressured him to embroider facts. Schmid says he is testifying against his former allies on principle because what he and they did was wrong.

Kurz denies perjuring himself, but said he testified under the extreme pressure of questioning from opposition lawmakers on the commission who, he argues, were trying to catch him out.

WHAT SENTENCE DOES KURZ FACE?

Up to three years in prison.

WHAT OTHER LEGAL TROUBLE DOES HE FACE?

Kurz is still under investigation, but has not yet been charged with corruption-related offences - the probe that led to his ouster.

Prosecutors suspect that, as part of a bid to get Kurz appointed leader of the conservatives when he was foreign minister, finance ministry allies including Schmid used public funds to commission fake polling that exaggerated support for Kurz, and buy favourable coverage in one newspaper.

The suspected offences, including bribery and breach of trust, are much more serious than perjury. Whatever the outcome, some damage to Kurz's reputation has already been done.

Leaked text messages in the investigation show Kurz using tactics that, while not illegal, have tarnished his image. They include looking to scuttle a potentially popular childcare plan because rivals including the then-vice chancellor, who was also leader of the conservatives at the time, would get the credit.

(Reporting by Francois Murphy; Editing by Angus MacSwan)