Well, he’s done it again. Ralph Nader, the outspoken consumer-rights activist and perennial presidential candidate, has thrown his hat into the 2008 election ring — and the outrage is already starting to fly.

Apparently unconcerned by his legacy among liberals as “the man who got George W. Bush elected,” Nader argues that the two-party system is fundamentally flawed and that his candidacy is a response to the failings of both Democrats and Republicans to address the real social issues facing the country.

While there is legitimacy to this message, we have to call his motivations into question.

Clearly, none of the causes Nader champions were helped by eight years of an administration that was elected by the narrowest of margins — margins well within the range of what Nader took in 2000.

To continue to engage in this quixotic campaign not only endangers real, viable change, it does irreparable damage to the the causes for which Nader fought so hard.

Ultimately, the biggest casualty of Nader’s involvement in the campaign is Nader’s own legacy. While older generations may still associate Nader with his successful — and important — campaigns to improve public safety and further government transparency, many younger people know him only as a spoiler and egotist, who skewed a crucial election.

That is unfortunate, because it casts a shadow over Nader’s earlier accomplishments, in a kind of “guilt-by-association” effect.

This is not to say that there is no place for marginal candidates in elections. Often, candidates with no real chance of winning can help bring balance to a public debate by airing issues that might not otherwise be injected into the race.

Candidates like Ron Paul and Dennis Kucinich have done exactly this, and the issues they have raised have made a positive contribution to the election.

But there’s a time and a place for such discussions. When it is clear that a candidate’s continued run for an office that cannot be won is likely to harm the very cause he or she is fighting for, it seems the very height of arrogance to press on anyway.

We find it disheartening that Nader would continue to do just that, tainting an otherwise admirable legacy of public service.