Call it BushCo's lunatic fringe strategery (sic) and Nader worship. Yeah, it's hard to believe, but Nader announced he's running again. In the American system, it's hard to buy votes directly, but lunatic fringes are the easiest to buy or divert. In terms of election strategy, it works quite well for BushCo. Dubya is perfectly willing to accept the votes of various lunatic fringes, and BushCo has the money to persuade their pet troublemakers NOT to run separately and suck off any of their votes. Meanwhile, the votes you can siphon off from your REAL opponents are just as useful as the votes you capture with lies or bribes.
In the current example, BushCo can covertly encourage fringe candidates like Nader to run on the other (progressive/liberal) side, thereby sucking off the lunatic fringes that might help offset the lunatic fringe votes they've collected for BushCo. I'm not saying that all Nader supporters are lunatics, but that's becoming his strongest base of support. Without him as an escape hole to toss their votes into, some of those fanatics would be willing to accept reality. Don't forget that Dubya's entire claim to legitimacy for his tyrannical redirection of America, his entire "mandate for change", comes down to 500 votes in Florida in 2000, as justified 5-4 by SCOTUS. (Never forget: "Our considerations are limited to the present circumstances." That's where history will file Scalia et al.)
You might want to cite Buchanan as some sort of exception, but he had no significant negative effect on Dubya in 2000, but, in a less-than-amusing twist of fate, purely by accident managed to have a significant negative effect on Gore in the crucial Palm Beach situation. Not the only crucial situation in 2000--but almost all of them broke against Gore.
Principles are important, but when your principles prevent you from seeing reality, you are insane. Gore is NOT equal to Bush. But even if the fanatical Nader worshippers wanted to say both of them were evil, Gore was VERY clearly the lesser of the evils--and one of them was going to live in the White House. Nader is serving NO constructive purpose now. In the three years since seizing power BushCo has already done more harm than all of the good Nader ever accomplished in his entire lifetime. Only insanity can explain Nader's divisive new campaign. It can only have two possible outcomes: it will assist BushCo in clinging to power or it will discredit Nader's beliefs and causes as far as the new Democratic president is concerned. President Nader is NOT a possible outcome.