It's no secret that Uber has its share of regulatory issues, so it's not exactly shocking that they've invested in a big name like David Plouffe to lead their lobbying and advocacy team. Hiring such a high-profile Democrat also strikes me as confirmation that the company regards its embrace as a partisan talking point by the GOP as potentially counterproductive.
But the fact that Uber is able to bring on a big gun like Plouffe shouldn't obscure something important — the company is massively outspent on politics by taxi industry incumbents.
Data published by Stan Oklobdzia of the Sunlight Foundation in late July found that "the taxi cab industry has donated at least $3,500 to the political war-chests of state legislators for every $1 that Uber, Lyft, and Sidecar gave." Hiring Plouffe is likely part of a larger strategy to step up political involvement that should close that gap. But if even the ridesharing industry were to double its contributions and then double them again, and then do it again, and again, and again, and again they'd still be massively outspent. And of course taxi incumbents can raise their spending in response to anything Uber does.