Those sounds you heard a few days ago turned out to be the exploding heads of Connecticut Democrats. During his announcement last week that he would not seek re-election, U.S. Senator Joseph Lieberman said that his politics were those of John F. Kennedy, a comparison that sent the state’s liberals into fits of enraged hysteria. I have no doubt that Mr. Lieberman sincerely believes what he said; in thirty years of state and national politics, no one has ever doubted his integrity. I suspect, however, that the maverick former Democrat also relished the opportunity to goad his old friends (and enemies) on the left.

Mr. Lieberman said that Kennedy’s policies—civil rights and social security, pro-growth economics and a strong national defense—were Lieberman’s policies and that, like Mr. Lieberman, President Kennedy might not “fit neatly into any of today’s partisan political boxes.” True, President Kennedy was initially distrusted by his party’s left wing, not least because of his father’s previous reactionary antics. Still it is hard to imagine Jack Kennedy endorsing the G.O.P. presidential nominee, as Mr. Lieberman did in 2008. Among other things, Kennedy knew that his constituents wouldn’t stand for it. Perhaps that’s how Mr. Lieberman is most different from his political hero. He has suffered in recent years from an acute political tone deafness of the sort that never afflicted Kennedy. As a result, Lieberman made some really bad political decisions, like speaking at the 2008 G.O.P. convention—perhaps the worst self-inflicted political injury since former House Speaker Tom Foley sued his own constituents.

One person’s tone deafness, of course, is another person’s profile in courage. Loyalty in friendship is a virtue, supporters might say, and Lieberman was simply helping a friend, John McCain, in 2008. Similarly, Mr. Lieberman’s “this-is-what-I-believe-the-consequences-be-damned” style of politics has a certain and admirable integrity. And while his Kennedy comparison is a stretch, there is some truth in it. Kennedy belonged to a time when Democrats and Republicans could stand to be in the same room together. People on both sides of the aisle not only could work together, but wanted to. Most of the last century’s progressive social legislation—not to mention civil rights—came about through coalitions of Democrats and liberal Republicans, the latter currently an endangered species, the political equivalent of the Klamath Chinook salmon. The evisceration of the GOP’s left wing by the Reagan revolutionaries, as well as the defection of the Democrat’s right wing to the G.O.P., has indeed led to a more stridently partisan, rigidly ideological politics. In Washington and elsewhere, moderation and compromise are viewed as vices and every political fight, however marginal, is an Ali/Frazier slugfest, frantically and cynically hyped by the Don Kings of cable news.

“I have not always fit comfortably into conventional political boxes—Democrat or Republican, liberal or conservative,” Lieberman said in his remarks. The problem with American politics at the moment is not that there are boxes, but that there are too few of them. One sometimes gets the impression that most people in politics see only two boxes, right and wrong. The relative ideological homogeneity in both parties has led to a kind of intellectual entrenchment that has dangerously impoverished our discourse. In a political system in which third parties are hard to start and even harder to keep going, this new, all-or-nothing-at-all politics, one that values purity of intention well above effectiveness of action, will lead inevitably to political stagflation: the nation’s business will come to a halt while the price of inaction grows daily.

Farewell, Mr. Lieberman. I have no idea whether you were the next John F. Kennedy. I doubt it. I sure do miss the old John Kennedy though, as well as the more effective and human politics that he practiced.