I always thought Ralph Nader was turned into an evil caricature. He was unfairly depicted as actively trying to get George Bush elected by pulling away votes from Al Gore in Florida. While I think it is fair to question his actions, I do believe Nader ran in 2000 for reasons at least he thought were just, and not with the express purpose of helping to elect Bush.
Ah, but what we have right now is SEIU threatening to become the bad caricature that Nader is only imagined to be. SEIU is now threatening to run third party candidates against conservative Democrats in swing districts that vote against reform. These are districts where most political analysts think the Republican candidate is likely to get just over or just barely under 50% of the vote in November. These are not primary challenges--because, in most cases, the filing deadline passed--but actual, third-party candidates.
While the SEIU claims otherwise, it is almost impossible to imagine that the point of these third-party candidates is anything but solely an attempt to draw votes away from the Democrats to ensure they lose their seats to their Republican opponents. This move does not seem to be about helping to elect third parties because, to my knowledge, it is not coupled with any broad push for the mechanism that would make third parties more viable (like proportional representation or instant run off voting). Nor is it targeted at heavily Democratic leaning districts where well-funded, progressive, third-party candidates might actually have a chance of winning.
Most importantly, SEIU is basically deciding to cast itself in the role of the Ralph Nader caricature that Democrats have been attacking as the ultimate evil liberal bogeyman for the last decade. Now, like the mythical, nefarious Nader Campaign--but unlike Nader's actual campaign--SEIU will run third-party candidates (who are right on all the requisite issues) with the express purpose of handing a Democratic seat over to the Republicans because the Democrat was not sufficiently "liberal" enough. I wonder what could have been achieved if the same hardball tactics were used to advance real progressive goals like a public option, single payer, drug re-importation, etc.
Personally, I understand the importance of political hardball and punishment. There is nothing that moves politicians like the fear that they will lose their next election. I even think our country would be much better off if we could move away from an almost completely two-party system. But this is a huge step by one of the nation's biggest unions.