Bill Bradley, however, is more than just a celebrity defector from a party in a mess. Wittingly or otherwise, he has become symbol of two realities of American public life: a growing disillusion among its more thoughtful practitioners at how two-party, adversarial politics currently function on Capitol Hill; and the increasing readiness of a frustrated electorate to look outside the system for independent candidates.
Those seeking firm commitments and the rhetoric of an incipient campaign did not gain much comfort from the senator. "Where the road leads, I do not know," he said, even as he noted that he was "not ruling out an independent route". Probably Mr Bradley is genuinely undecided. But as the endless speculation about the plans of General Colin Powell testifies, rarely has America's political terrain been as favourable to an independent candidacy.
Bill Bradley is but the latest potential recruit to a cause stretching back at least as far as John Anderson, who won 6 per cent of the vote when he challenged Ronald Reagan and Jimmy Carter in 1980. Well before Mr Bradley, prominent senators of both parties, like the Republican Warren Rudman and the Democrat Timothy Wirth, decided that the game was no longer worth playing. And all the while, the disaffected centre has grown, culminating in the extraordinary 19 per cent of the popular vote garnered three years ago by Ross Perot.
Mr Perot would still attract over 15 per cent this time round. The same polls moreover show that at least as many Americans consider themselves independents as Republicans or Democrats, and that up to half the electorate would welcome a third choice if the main party contenders next year are a distrusted Bill Clinton and an uninspiring Bob Dole.
Thus does the pool of non-aligned voters seeking a "new politics" steadily grow, and so does the number of those who offer it. At the very moment Mr Perot entered the 1992 contest, Paul Tsongas briefly led the chase for the Democratic nomination, warning in his austere cross-party "Economic Call to Arms" of the disaster looming if America did not put its financial house in order.
The former Massachusetts senator is now an unabashed independent. The Concord Coalition he leads with Mr Rudman crusades for a balanced budget, while Mr Tsongas has publicly urged Gen Powell to run. Mr Perot dances on the edge of a second run, while Lowell Weicker, a former Republican senator who was elected Governor of Connecticut as an independent, is mulling a challenge.
Not that the task will be easy. Gen Powell has yet to decide whether he will run and the prevailing punditry is that he will not. His supporters, a group called Citizens for Colin Powell, last week filed papers with the Federal Election Commission that will allow them to become a fully fledged campaign committee. But that is only the start. Money must be raised, local organisations put together, and signatures collected to have his name on the ballot in all 50 states. Gen Powell is often called a "Black Eisenhower" but that last military man to become President did so as a Republican, able to draw on the existing structure and resources of the party.
Most important of all, Gen Powell has yet to deal with the actual issues. The solution, he declares in his standard lecture-circuit speech, "isn't some new programme or more government ... it's not screaming at our politicians or watching them scream at each other".
But what the solution might be, thus far he is not saying. And why should he, one might ask, given (if US News & World Report is right) his rating of 71 per cent?
Nor has he ever disclosed his party allegiance, though these are assumed to be marginally Republican. In any case, in putative three-way match- ups, he takes more votes from Senator Dole than from Mr Clinton, allowing the latter to win a narrow plurality. Unsurprisingly, the President's campaign strategists believe that a Powell run this time could be Mr Clinton's best chance of keeping the White House, just as Mr Perot helped give him it in 1992.
A Bradley candidacy would be different, taking moderate Democratic support from Mr Clinton, just as a run by the Rev Jesse Jackson would eat into the Democratic constituencies of blacks and other minorities. So, war- gamers of the independent cause might reckon, why not combine Gen Powell and Mr Bradley into an up-market "Dream Ticket" that would surely be invincible? And is the idea so far-fetched? After all, the senator acknowledged last week he had "been in touch with" the general about his decision. And, given the electorate's enduring frustrations, what thoughts could be more natural?