Ralph Nader’s surprise Sunday-morning announcement when probed on “Meet the Press” that he’ll indeed run a fifth time for president as a third party candidate is mostly flabbergasting the left.

Journalist James Fallows, who penned two books working for Nader in the 1970s, calls Nader’s jumping in a farce. “I will always like and respect Ralph Nader,” he writes at his Atlantic Monthly blog. “But I wish to God that he had not made this decision, or will reverse it soon.” A popular YouTube video warns Nader (amid slight profanities): “You gave us OSHA and the EPA and seat belts. We freaking love seat belts. . . . But Ralph, Ralph, Ralph—if you run this time, you can stick those seat belts where the minimum wage don’t shine.”

RalphDontRun.com, an awareness site run by John Pearce, argues third-party candidacies have “the inevitable effect of helping elect those most hostile to one’s agenda.” Pearce supports Barack Obama because he fears a Clinton ticket would encourage left-leaning voters to cast ballots for Nader. “The ultimate irony of the situation is this: both the Republicans and Ralph Nader are desperately rooting for Hillary Clinton as their best hope for 2008,” he writes on his site.

Clinton may outdo Obama here, but many right-of-center pundits argue that having Nader in the race is good no matter what. “Today’s Democratic climate is in some ways a product of the anti-corporate, pro-outsider zeal that’s defined Nader’s public presence,” Abe Greenwald writes at Commentary’s blog Contentions. “The Democrats’ change mantra, pacifist imaginings, demand for universal healthcare, anti-lobbyist fervor, environmental hysteria, and young voter turnout all spell good news for Nader.” Let’s-return-to-the-gold-standard fringe thinker Ron Paul’s ability to crossover party lines and pull around 5 percent of the vote in many states may also be energizing Nader, though critics say Democratic Rep. Dennis Kucinich’s inability to be taken seriously in his bid should temper that thinking. (Paul said again Sunday that he absolutely won’t run as a third-party candidate.)

Not everyone on the right is convinced Nader will matter. “[Obama] out-lefts him, Al [Gore] out-greens him, and Hillary out-scolds him,” writes John Derbyshire on National Review’s blog The Corner. Nader bests McCain’s 71 years by two, making him the oldest in the field, and has run perennially, and unsuccessfully, for president on the same platform for two decades. “Go home, Ralph,” Derbyshire says.

Many Democrats agree—those who feel enthused about their chances for 2008, still wary from Bush v. Gore in 2000 and possibly sore that Nader’s candidacy contributed to Bush’s entrée to the White House. The role Nader’s 97,488 Florida votes played in spoiling 2000 is still hotly debated; yet a Paul third-party gamble would certainly cull Republican votes, and the same is assumed for Nader. Obama’s campaign site features a page for Nader fans who threw their support behind Obama in Nader’s absence. If loyalties shift back, it could be telling for Nader’s chances.

The two wasted no time butting heads. Nader skewered Obama for “leaning toward the pro-corporate side of policy-making” and flip-flopping on his pro-Palestinian stance. Obama retaliated that Nader’s “function as a perennial candidate is not putting food on the table of workers.”

Interestly, Obama has old-time ties to Nader. In his memoir Dreams from My Father, Obama writes that after graduating from Columbia University in 1983, he “needed a job closer to the streets. I spent three months working for a Ralph Nader offshoot up in Harlem, trying to convince the minority students at City College about the importance of recycling.”