The only principle that I adhere to is that of progress. Sometimes, you must sacrifice utopia for progress. This is what folks like David Sirota and Jane Hamsher don't understand. You're either with them, or you're an evil corporatist, imperialist, or a plain old useful idiot.
There is one group of people who will have no right to complain when the Supreme Court strikes down (or effectively nixes) section 5 of the Voting Rights Act: any progressive who has ever voted for a third party candidate for President. Had the 96,000 Naderites in Florida decided to live in the real world, and voted for Al Gore in 2000, we wouldn't be facing this looming disaster.
So the next time you decide to vote against the Democratic candidate for President or US Senate in your state because of [insert anti-"system" platitude here], remember the good old days of the Voting Rights Act. I don't know who Al Gore would have nominated to the Supreme Court, but I'm almost certain it wouldn't have been John Roberts and Samuel Alito.
We don't live in a multi-party system. There are only two parties now, and will be for the foreseeable future. There is a centrist party, and a party that denies that humans contribute to global climate change and that guns kill people. You only get to choose between these two groups---who would you rather have nominating Supreme Court Justices?