From Time Magazine's How Audi is Cleaning Up with Clean Diesel's question and answer with Johan de Nysschen, president of Audi's U.S. division:

Audi is instead touting the benefits of diesel technology. How do you get around the negative perception of diesel cars in the U.S.?
Clean-diesel technology represents an immediate technological leap — you immediately, very significantly, reduce fuel consumption and emissions. Biodiesel, too, could get you very close to the point where you can have a neutral carbon footprint. This can all be attained in a relatively shorter space of time, and at lower costs, than waiting 20 years–plus until we get our act together with electric cars. I should say, though, that hybrids are important. It is not diesel vs. hybrid — they are complementary technologies. We, too, will be producing hybrids — diesel ones.

Given the driving patterns of most American consumers, which is more likely to be suburban travel, clean diesel has advantages. Because this technology holds so much promise, it's our task to inform the public and policymakers because it's clear that public [opinion] will have to embrace all available technologies to move things forward. I also listen to all of our dealers, and it's very clear that those consumers who are informed about the technology have really embraced it with great enthusiasm.

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