He seems fairly left-wing. For instance, he supports single-payer. His position of taxing capital gains at rates higher than normal income taxes is also fairly radical, and even I can't really support that. While I suppose it would be ideal to have the taxed equally, we also need to keep in mind tax competition with other countries.
A raise from 15% to 20% or 25% may not cause much of a ruckus, but without agreements from all of the major economic powers to equalize income and capital gains at the same time, any such radical increase (from 15% to 40% or so for the most wealthy) would likely lead to capital flight. However, in any case, he'd likely have to compromise and change his position if the issue were seriously being discussed, so I suppose it's not a huge deal.
As for Citizens United (and the, in my mind, more important case of Speechnow.org v. FEC, which allowed for SuperPACs), the most practical way to deal with this case would be to support presidential candidates who promise to appoint supreme court judges that will repeal it. A constitutional amendment is really unnecessary, and not likely to pass, because their is a good argument that the supreme court overstepped it's bounds in substituting it's judgement that there was no danger of quid pro quo arrangements and corruption from such a state of affairs for that of the legislatures. The ruling was 5-4, and it's also rather recent and doesn't have the weight of precedent behind it. I personally don't think it will stand the test of time.
