Romance between two leading figures of Germany's Left party has boosted interest in the party as it tries to keep its foothold in national politics.

She -- Sahra Wagenknecht -- is the fiery 42-year-old deputy leader of the Left party, while he -- Oskar Lafontaine -- is the 68-year-old former Social Democrat (SPD) leader who famously defected to the hard left in 2005, to the fury of his former party.

He wants a comeback, she wants to advance, Germany's Stern magazine wrote in its online edition on Monday, naming them a pair with a mission.

The Left party has fallen to eight percent in opinion polls from its showing of almost 12 percent in 2009's federal election.

Wagenknecht and Lafontaine already appear regularly in media and on chat shows. She could become party leader next year, he the lead candidate in the 2013 federal election, the speculation runs. The party is set to elect a new leader next year.

When two celebrities get together, they do not simply double their public impact, they multiply it many times over, media psychologist Jo Groebel told Focus magazine.

Wagenknecht, dubbed the beautiful Communist by the mass-circulation newspaper Bild, has been compared to the historic heroine of the German left, Rosa Luxemburg, as she wears her hair swept up and favours long, flowing skirts.

Luxemburg helped lay the foundations for Germany's Communist party and was murdered by right-wing paramilitaries in 1919.

Lafontaine is a veteran of the German political scene, heading the SPD and serving as finance minister in the centre-left government of Gerhard Schroeder before the pair fell out.

He later helped forge the Left Party from disgruntled left wingers of the SPD and former East German Communists. He was long seen as Wagenknecht's mentor.

The married Lafontaine stunned delegates at a party conference on Saturday when he announced: I have been living separately for some time, and have been in a close relationship with Sahra for some time. That's that. I have nothing more to say about it.

Wagenknecht is also married, to film director Ralph Niemeyer. He wrote in his blog that the marriage had already moved into a love based on friendship.

When Sahra told me about Oskar, this was not a shock for me, rather it was more or less expected, he wrote. But if she'd told me that the object of her desire was Helmut Kohl, then I would have shot myself with an air gun.

(Reporting by Alexandra Hudson)