His name was Kennedy. He was the preeminent figure in the Democratic Party. And he was a resolute supply-side tax-cutter.

“It is a paradoxical truth,” he once told the Economic Club of New York, “that tax rates are too high today and tax revenues are too low and the soundest way to raise the revenues in the long run is to cut the rates now.” What he had in mind, he said, was “an across-the-board, top-to-bottom cut in personal and corporate income taxes.”

Those were not the words of Senator Edward Kennedy. The speaker - in December 1962 - was President John F. Kennedy, and his ringing call for tax cuts was no anomaly.

Four months earlier, JFK had called high tax rates a danger to “the very essence of the progress of a free society.” In his 1963 State of the Union message, his first priority was “the enactment this year of a substantial reduction and revision in federal income taxes.” In the speech he was scheduled to deliver on Nov. 22, 1963, Kennedy planned to report proudly: “We have proposed a massive tax reduction, with particular benefits for small business.”

In recent days, Ted Kennedy has been justly acclaimed as a lion of the Democratic Party. But how different the party mourning Kennedy today is from the one that nominated him in 1962.

The reversal on taxes is one vivid example. When Ted Kennedy first entered the Senate, it was Democrats who campaigned for sweeping tax relief that would eventually slash the top marginal rate by 21 percentage points. But Democrats have long since become the party that resists lower taxes. Now it is Republicans like George W. Bush who champion JFK-style rate cuts - cuts that Democrats now condemn as “tax breaks for the wealthy.”

On civil rights, too, there has been a sea change.

Liberal Democrats in the 1960s upheld the colorblind ideal - the conviction that Americans should be judged not by the color of their skin, but by the content of their character. Far from supporting racial quotas and preferences, civil-rights Democrats flatly rejected them. Senator Hubert Humphrey vowed that if anyone could find anything in the 1964 Civil Rights Bill that would compel hiring on the basis of race, “I will start eating the pages one after another.” In a 1963 press conference, President Kennedy explicitly opposed racial preferences: “We are too mixed, this society of ours, to begin to divide ourselves on the basis of race or color.”

But in the years that followed, as such preferences became entrenched in hiring and education, liberal Democrats became their doughtiest supporters. When the Supreme Court ruled against the racial classification of schoolchildren in 2007, saying “the way to stop discrimination on the basis of race is to stop discriminating on the basis of race,” Kennedy blasted the decision as one that “turns back the clock on equality.”

Especially dramatic has been the Democratic Party’s metamorphosis on national security.

“There are some who say that communism is the wave of the future: Let them come to Berlin,” declared President Kennedy, a staunch Cold Warrior, in his great Berlin Wall speech in 1963. By 1987, when another US president journeyed to Berlin to challenge Moscow to “tear down this wall,” such muscular anti-communism had all but vanished from Democratic Party thinking.

JFK likewise spoke for mainstream Democrats when he asserted that America would “pay any price, bear any burden” to advance freedom and democracy in the world. He was a hawk who pressed for higher defense spending and American military superiority. The Democratic Party of more recent years - the party of “come home, America” and the nuclear freeze - was one he wouldn’t have recognized.

All political parties alter over time, of course. Today’s Republican Party is not a carbon-copy of Eisenhower’s: It is more internationalist, more religious, more Southern. But a resurrected Eisenhower would still recognize the GOP, and still command its esteem.

The Democrats’ transformation has been much more profound. Over the course of Ted Kennedy’s long Senate career, his party’s ideological center shifted hard to the left. It goes without saying that a JFK today could never be the Democrats’ presidential candidate. The question is, would he still be a Democrat?