I used to hold Dick Cheney in high regard. I met him 25 years ago when I was part of the Washington Semester program at American University in Washington. Class often consisted of meeting with members of Congress and government representatives - usually informally in their offices.

Of the many outstanding interactions, one was truly exceptional. I can still picture the obscure sole member of Congress from Wyoming - who at age 34 had been President Gerald Ford's chief of staff - perched at his desk with his cowboy boots in full view, lecturing to a small group of us about the world.

Cheney was impressive in his remarks and gracious with his time. Since that day, I've maintained respect for the man who has served his country for the better part of four decades as White House staffer, congressman, secretary of defense, and vice president. Even when disagreeing with him, I've abhorred the Darth Vader image favored by some.

Now he's losing me. By using a 90-minute interview with Politico to preemptively criticize President Obama's decision-making process regarding Afghanistan, Cheney sought to undermine the commander in chief the night before the most important foreign-policy announcement of his young presidency.

That the former vice president said Obama was projecting "weakness" was bad. Worse was when he suggested that Obama was "far more radical" than expected on some foreign-policy and national-security issues, which was wholly over the line.

It is not always Cheney's message with which I disagree. I happen to concur with his defense earlier this year of harsh interrogation methods. My objection is to the messenger and the timing. Whatever he says carries the imprimatur of the office he once held, and speaking up at critical junctures undercuts the president before his policies can take hold.

It also places Cheney at the wrong end of the spectrum among an important constituency: the fraternity of retired White House occupants, including the man he served alongside for eight years.

While Cheney's disapproval has been almost constant, George W. Bush has remained true to the words he spoke during his first post-presidency speech last March: "I'm not going to spend my time criticizing [Obama]. There are plenty of critics in the arena. He deserves my silence." And indeed, aside from a few faint jabs during a June speech in Erie, the only "arena" Bush has entered involved throwing the first pitch for the Texas Rangers and participating in the coin toss for the Dallas Cowboys.

That approach is more in keeping with American tradition, according to presidential historian and author H.W. Brands. In June, Brands was one of nine prominent American historians - others included Michael Beschloss, Doris Kearns Goodwin, and Douglas Brinkley - to attend a White House dinner where Obama sought historical perspective on the office he now holds.

During a phone conversation last week, Brands told me: "Generally speaking, retired presidents stay out of day-to-day politics. They give speeches sometimes, but the speeches usually don't touch on current controversies. There's been a feeling that retired presidents form a very exclusive club, and they know the responsibilities of the office. They can remember what it was like when they were in office and the last thing they needed was one of their predecessors taking pot shots at them."

That's not to say that former presidents and vice presidents have never criticized their successors. George W. Bush himself endured plenty of disapproval from Democratic former commanders in chief, especially Jimmy Carter, who once called W's presidency the "worst in history."

But that comment came in May 2007, deep into Bush's second term, months after the Iraq surge had been announced, and more than a quarter century since Carter held office. It wasn't right. But the degree and circumstance were different than Cheney's most recent outburst. Indeed, slinging such high-profile criticism on the eve of such a significant national-security speech, Brands told me, is "pretty much unprecedented."

"I can't think of anything close to this," he said. "Generally speaking, people who have held the highest offices in the land, president and vice president, have sufficient respect for what their successors have to do, and how the actions of any president impact on national security, that they're usually quite loath to make anything like a partisan issue of big national-security policies."

And unlike many of his vice-presidential predecessors, Cheney is at this point beyond the realm of future political ambition, Brands noted.

"I think it's important to note that we're really talking here about good or poor taste. There's nothing obviously in the Constitution or American law that says a retired president or vice president can't speak his mind. This is in the tradition of American freedom of speech," he said. "The question is whether it's in good taste, whether prudentially they ought to exercise that right."

Time and a place, my parents often said. Time and a place.