Among established luxury brands, Porsche may be among the best equipped to challenge Tesla Motors.

The German automaker known for its sports cars has already built three plug-in hybrids, beating Audi, BMW, and Mercedes-Benz to launch that powertrain in the large luxury sedan and mid-size crossover segments.

And there have been persistent rumors that it will follow those up with an all-electric sedan of some kind.

DON'T MISS: How Audi, BMW & Mercedes Plan To Compete With Tesla--And Why

The latest is a report from French car magazine L'Automobile saying that an electric Porsche concept car will appear at the 2015 Frankfurt Motor Show in September.

This concept is expected to preview the "Pajun"--Porsche's rumored mid-size luxury sedan.

That code name is short for "Panamera Junior," denoting the new model's slot below Porsche's existing full-size sedan in the lineup.

2015 Porsche 918 Spyder

2015 Porsche 918 Spyder

The Pajun--which is likely to be offered with internal-combustion powertrains as well--will likely compete with models like the Audi A6, BMW 5 Series, and Mercedes-Benz E-Class.

That means it should be close in size to the Tesla Model S as well.

While Porsche hasn't yet shown any all-electric cars in public, there's been plenty of speculation about its plans for them.

ALSO SEE: Porsche Electric Sport Sedan To Target Tesla In 2018, Fuel-Cell Version To Follow?

Rumors of an all-electric Pajun variant have circulated for the past year or so, fueled recently by the discovery of patent drawings showing how the car's platform could be adapted for battery--and even hydrogen fuel-cell--power.

There have also been reports of a smaller Porsche electric sedan called the 717.

If they're to be believed, the 717 would be a dedicated electric model, with more coupe-like styling than the Panamera or Pajun.

2015 Porsche Cayenne S E Hybrid

2015 Porsche Cayenne S E Hybrid

Some also point to a presentation given by Volkswagen Group technical chief Ulrich Hackenberg earlier this year as a hint at possible electric-car plans.

A chart showing plans for future battery-electric and fuel-cell models for VW Group brands included one of each for Porsche.

None of that really constitutes concrete evidence, but the appearance of an electric concept car in Frankfurt this fall would certainly make a compelling statement.

MORE: New, Smaller Porsche Four-Door Sedan To Be Electric Only: Rumor

Reports indicate that of all the German makers, Porsche was the most rocked by the relatively sudden emergence of the Tesla Model S as a viable, high-performance luxury vehicle--one that, in 2013, Porsche could not directly match with any product then in production or even planned.

The Pajun is expected to enter production in 2017 or 2018.

Stay tuned to see if an electric version appears then.


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