Comparisons between Iraq and Vietnam are frequent, but the battle over the war may soon have something in common with another dark event: Watergate. That would be the moment when leading members of the president’s own party go to the White House and tell him enough already.

That’s what happened Aug. 7, 1974, when Barry Goldwater and other GOP leaders met privately with President Richard Nixon. Articles of impeachment had been approved by the House Judiciary Committee, and the angry tide in Congress and the public was about to sweep him away.

Goldwater, an elder statesman and party “bull,” emerged from the meeting to deny the group had urged Nixon to quit. In a masterful understatement, he said they merely reported “what we see as the conditions” in Congress. Another senator chipped in helpfully with the math: Nixon could count on only 10 or 15 GOP votes in either house. The next day, Nixon announced his resignation.

No, George Bush is not facing a serious threat of impeachment, and this is not a call for him to resign. But we are witnessing a tipping point in his presidency. His war management is so unpopular that even rank-and-file Republicans are criticizing him. The White House has responded with an arm-twisting campaign that argues that opposing the president on Iraq is bad for the troops, bad for America, and will destroy the GOP.

Once again, Bush has it perfectly backward. Just as his decision to send 21,500 more troops into harm’s way is the wrong response to the failures of the Iraqi government, his demand for party loyalty is misguided. At this late stage of the Iraq debacle, resistance is both right and noble. Only by standing against their president will Republicans be putting country ahead of party. Perhaps they will be able to lead Bush to a more sensible course, one more Americans can support and one that holds a better chance of success.

Fortunately, some are rising to that challenge. And none is more suited to the task than Sen. John Warner.

The Virginia Republican is playing the role of the Greek chorus in the Washington drama, somberly delivering the grave news that public support is gone and warning of more tragic consequences. With polls showing two-thirds of Americans against sending additional troops, Warner has boldly co-sponsored a resolution opposing the surge.

His earned authority was on full display at the Armed Services Committee hearing last week. In a courtly lecture to Lt. Gen. David Petraeus, the new Iraq commander, Warner recalled his days as secretary of the Navy during Vietnam 35 years ago. He said the political crossfire of Iraq “brought it all back,” especially the sense of a nation pulling away from the president and his policy.

He warned Petraeus to “review the transcript” to make sure he had not accused those who oppose the surge of aiding the enemy and reminded Petraeus that Bush had invited new ideas. In that spirit, Warner asked, “Why can’t the Iraqi forces handle Baghdad and the sectarian violence?” He suggested that more of our forces be deployed to areas where the insurgency is the main problem, such as Anbar Province.

Those ideas are on target, and Warner’s message was unmistakable: We are giving the president our best advice, and we will not be silenced by rancid charges of treason.

Some critics are not satisfied with that approach and are calling for cutting off funds. That’s a mistake, one that really would hurt our troops and our cause.

A better way is for Democrats to go slowly and for Republicans to join with Warner in delivering the truth to Bush personally. Mr. President, they can say, it is time for you to listen. You must change course, or you will be alone. And then nobody can save you or our cause.

That day, and that message, are now our best hope.