PLYMOUTH --MAYBE ITS SOMETHING congenital when it comes to the Kennedys and Richard Nixon. Here is how Congressman Patrick Kennedy (D-R.I.) began his remarks on the war in Iraq during the recent debate in the House:

“My uncle said a generation ago, ‘as we examine the history of the conflict, we find the dismal story repeated time after time. Every time and every crisis, we have denied that anything is wrong, sent more troops and issued more confident communiqués. Every time we have been assured that this one last step would bring victory, and every time the predictions and promises have failed, have been forgotten, and the demand has been made again for one more step up the ladder. And once again the president tells us that we are going to win — victory is coming.’

“My uncle, Robert F. Kennedy, made this statement in March of 1968. It took another five years, and 37,544 American lives, before a United States president was withdrawing Americans out of Vietnam and stopping that war.”

Some of us older than Kennedy, who was born in July 1967, remember Nixon’s actions a bit differently. Far from waiting five years “before” withdrawing American troops from Vietnam, a war he inherited from two Democratic presidents, including another of Kennedy’s uncles, Nixon waited all of five months.

In June 1969, Nixon declared the first withdrawal of 25,000 troops to be completed by the end of summer — followed by an announcement in March 1970 to pull out another 150,000 troops in 12 months — followed by Nixon vowing in April 1971 to send home another 100,000 troops by year’s end.

By the spring of 1972, “Vietnamization,” the policy of transferring responsibility for fighting the war to the South Vietnamese government, reduced American troop presence to 70,000, of which 6,000 were combat troops, from the more than a half-million troops inherited by Nixon in 1969.

Not surprisingly, the communists exploited the shrinking American presence by launching a major offensive in March 1972. Undeterred, Nixon continued shifting responsibility for the war to South Vietnam. Voters showed their appreciation by overwhelmingly re-electing Nixon that fall. He won 49 states while his opponent, Sen. George McGovern, could claim — go figure — only Massachusetts.

Congressman Kennedy also skirted any mention of the context of his late uncle’s remarks on Vietnam, though in fairness to Kennedy, he could not reasonably be expected to provide much detail on this in the five minutes that House members were each allotted.

Robert Kennedy’s criticism of President Lyndon Johnson’s handling of the Vietnam War, his nephew pointed out, came in March 1968. Two months earlier, RFK had ruled out running for president that year. His announcement came just before the Tet Offensive, a major communist onslaught across South Vietnam, and the reaction to Kennedy’s decision was just as immediate.

RFK “was brutally ridiculed on two prime-time comedy shows — Rowan and Martin’s Laugh-in and The Smothers Brothers Comedy Hour . . .” — the Jon Stewarts of their day — “ . . . for, in effect, chickening out,” wrote biographer Evan Thomas in Robert Kennedy: His Life.

With the anti-war candidacy of Democrat Eugene McCarthy fast gaining momentum, and CBS anchor Walter Cronkite expressing doubts about America’s prospects in the conflict, Kennedy agonized for weeks. In mid-March, after McCarthy had bloodied LBJ in the New Hampshire primary, finishing a strong second to an incumbent president (49 to 40 percent), Kennedy jumped into the race in a matter of days. Two weeks later, LBJ declared that he would not seek re-election. That fall, after Democrats nominated Hubert Humphrey over McCarthy, Nixon was elected president.

Considering the circumstances, it is not surprising that Patrick Kennedy decided against mentioning the context of RFK’s remarks. They were made as Robert Kennedy launched a challenge to oust an incumbent president of his own party. Such a decision is never made lightly, because the party infighting to follow, and 1968 is a textbook example, often succeeds only in getting another party’s candidate elected.

From a Democratic perspective, things could hardly have gone worse following RFK’s reversal. Both he and Martin Luther King Jr. were gunned down by assassins within months. The Democratic convention in Chicago that summer was a televised embodiment of anarchy. After Nixon was elected in November, only one Democrat would win the presidency in the next 24 years.

Yet even after the disastrous aftermath of RFK’s decision, a similar one was made 12 years later, with similar results — by Patrick Kennedy’s father. Just as RFK had grown disenchanted with Johnson, Edward Kennedy had with President Jimmy Carter. In November 1979, Kennedy announced he would challenge Carter, an incumbent Democratic president. A year later, voters elected Republican nominee Ronald Reagan.

Just as a major foreign-policy debacle closely dovetailed with RFK’s announcement, so it was with Edward Kennedy — Iranian militants seized American hostages in Tehran days before he formally announced, quickly altering the dynamic of what became an abysmal campaign for Kennedy. RFK’s campaign in 1968 came at the cost of his life. Edward Kennedy’s campaign in 1980 killed whatever dreams he had of reviving Camelot.

Patrick Kennedy’s remarks on Iraq contained another curious omission — no mention of his October 2002 vote in favor of authorizing military force against Iraq. Once again, Kennedy was following the example of “my uncle,” Robert Kennedy — another Democratic hawk, at least initially.

Jack Coleman, an occasional contributor, lives in Plymouth, Mass., and writes about politics at leftwingescapee.com.