Rep. Jack Murtha of Pennsylvania calls for withdrawal of troops from Iraq "at the earliest practicable date."

In 1967, Tip O'Neill, no liberal on defense, stunned President Lyndon Johnson by telling him that the Vietnam War had become a lost cause.

In 1968 Walter Cronkite, "the most trusted man in America," after returning from a trip to Vietnam during the Tet offensive, called for the withdrawal of U.S. troops during a prime-time special on CBS.

After the piece aired, President Johnson said, "If I've lost Cronkite, I've lost middle America."

Howard Fineman in Newsweek, in an article partially entitled "Bush at the Tipping Point," describes Rep. Murtha as "the one-man tipping point."