Senator Lieberman’s decision to retire from the Senate after four terms is a tragedy for the Democratic Party, particularly for the party of President Kennedy, who 50 years ago today gave the inaugural speech that inspired Mr. Lieberman’s career. The senator’s retirement is a tragedy for the rest of America, too, but America will survive. Whether a Democratic Party that finds itself unable to make a home for the likes of Mr. Lieberman will survive, that is, at least by my lights, less certain.

I offer that thought with a sense of sadness. As recently as the mid-1990s, when I was editing the Forward, I was quoted by the Chicago Tribune as describing myself as a “Kennedy liberal.” I sent them a letter to the editor saying, “I’d better note that the Kennedy in question was JFK — i.e., I am a hawk on Vietnam, want an activist foreign policy, support the gold standard, favor supply-side tax cuts and believe in aggressive federal support for civil rights short of quotas.”

One can argue that Mr. Lieberman is the last Kennedy liberal in the Congress. The last actual Kennedy, of course, was Senator Edward Kennedy’s son, Patrick, who decided not to run again and last month went home to Rhode Island. But Mr. Lieberman looks like the last Kennedy liberal — a strong supporter of civil rights, liberal but not too liberal on social issues, a supporter of supply-side tax cuts, and a Democrat prepared to carry any burden, oppose any foe, support any friend to ensure the survival of liberty.

Not even Mr. Lieberman had the complete kit. Kennedy’s support for the gold standard — or at least the version of it that existed in the 1960s — comes to mind. Kennedy spoke about it at, among other places, his 39^th press conference, in July of 1962, when the dollar still had the value of a 35^th of an ounce of gold, when he was under pressure to devalue. He said that he wouldn’t. He wanted, he said, a dollar “as good as gold.” Instead, to boost the economy, he would unveil his famous tax cuts at the top margin of the tax scale.

Senator Lieberman, in any event, has more of JFK on the substance than other major Democrats today. What he cited when he announced his retirement was JFK’s inaugural speech. That was the speech in which the newly minted president, our 35^th, exhorted us not to ask what our country could do for us but what we could do for our country. It was when he spoke of carrying any burden to ensure the success of liberty. And when he spoke of the belief of our Founders that “the rights of man come not from the generosity of the state, but from the hand of God.”

What Democrats talk like that today? The last president to talk like that was George W. Bush. He used to talk about how the yearning for freedom was universal because it was given to man by God. He talked like that through his whole presidency. On the eve of Mr. Bush’s second inaugural, The New York Sun wrote about the similarities in an editorial called “John Fitzgerald Bush.”

Mr. Bush proceeded to deliver a speech in which he declared that the goal of the United States would be nothing less than “ending tyranny in our world.” He also spoke directly to those fighting for freedom in other countries and said: “When you stand for your liberty, we will stand with you.” How those vows infuriated the Democrats and the post-Kennedy liberal intelligentsia, who spoke of Bush’s “hubris” and “over-reaching” and complained of how his speech was “extraordinarily ambitious” and “aggressive.”

When push came to shove in the war in Iraq, the Democrats bailed out one after another, save, in the end, for Joe Lieberman. He was practically the only Democrat prepared to bear the kind of burdens Kennedy spoke of bearing in the cause of liberty. For his sins he promptly lost the nomination of his party in Connecticut and had to suffer the indignities of running as an independent. Even his friend Hillary Clinton, then a senator, abandoned him.

When he won, he caucused with the Democrats, but the breach was more than political. Oh, the Democrats made nice to him when it looked like they might need his vote to organize the Senate, in which, with almost Shakespearean drama, he ended up holding up a deciding vote. But the notion that the breach was irreparable was verified with Mr. Lieberman’s decision not to seek a fifth term. Who among the Democrats today would hold aloft the kind of torch for freedom throughout the world that JFK did in his inaugural?

The symbol of the Obama doctrine has been captured in the photographs of President Obama bowing to foreign leaders, in the long resistance to tax cuts, in the frantic pursuit of a weaker dollar. When earlier today a ceremony was held on Capitol Hill to mark the 50^th anniversary of Kennedy’s inaugural speech, the television audience — and many in the building — had to be wondering what the Democrats were thinking.

This evening Mr. Obama is due to be at the Kennedy Center for the day’s second major event to honor JFK’s inaugural address. Where was he the night before? Feting the Chinese communist Party leader, Hu Jintao, the hammer of Tibet, at the White House. The fact of the matter is that within the Democratic ranks, there is really only one who still believes in the themes Kennedy sounded at his famous inaugural, and all too soon, Mr. Lieberman will be gone, and the loss will belong to the Democrats.