Anti-war Congressman John Murtha of Pennsylvania is prominent among some Democrats in his use of the "I" word -- impeachment -- about President George W. Bush and Vice President Dick Cheney. Murtha made his comments on CBS's "Face the Nation" and elsewhere.

Few serious observers think things will ever get to actual impeachment. And yet the American public seems more open to the concept than many imagine, according to a new national poll. The implications of this public sentiment could be huge for the 2008 presidential elections.

Our InsiderAdvantage/Majority Opinion poll asked this:

"Would you favor or oppose the impeachment by Congress of President George W. Bush and Vice President Dick Cheney?"

Favor: 39 percent.

Oppose: 55 percent.

Undecided/Don't Know: 6 percent.

The survey of 621 registered voters has been weighted for age, race, gender and political affiliation. The poll has a margin of error of plus or minus 4 percent.

About four out of 10 Americans favor impeaching the president and vice president. But the biggest news from this survey is not the overall results, but the opinions of independent voters, who usually decide presidential elections.

Forty-two percent of independents want Bush and Cheney impeached. These aren't just voters who disapprove of the White House. Instead, they're for initiating a process that could remove them from office.

To help put these startling numbers into perspective, I turned to the man most identified with the impeachment of Bill Clinton in the 1990s, former Congressman Bob Barr.

Recall that Barr initiated the Clinton impeachment process by filing what's called an "Inquiry of Impeachment." That's a resolution that precedes an actual "Bill of Impeachment." In the case of Clinton, it was filed long before anybody had heard of Monica Lewinsky.

Analyzing the InsiderAdvantage polling numbers, Barr said, "This indicates the surprising depth of dissatisfaction with Bush.

"I'm not sure we -- [the leaders behind Clinton's impeachment] -- ever really had hard polling numbers in favor of impeachment that were this high when we were in the midst of the process. Perhaps, but I don't recall it."

Those few in the Democrat-controlled House who are advocating impeachment are on the fringe of political thought -- at least for now. That's probably justifiable. Their reasons for impeachment look specious.

Yet one can't help but recall that Barr sounded like a lone voice in the wilderness when he first targeted Clinton. And one of his "charges" against President Clinton was the catchall accusation of "violation of oath of office."

It's not beyond consideration that what now seems silly political grandstanding could get much more serious, especially if the Iraq war continues to go badly, current scandals surrounding the attorney general or White House political adviser Karl Rove get worse, or new White House scandals emerge.

Be all that as it may, the main significance of this public opinion survey isn't its potential predictive value regarding the careers of Bush and Cheney. Rather, the poll tells us that the Republican team readying to assume the party's mantle when the presidential campaign kicks off in earnest in the summer of 2008 might be facing insurmountable odds.

Independent voters are the critical demographic in key swing states such as Florida and Ohio. We track this segment of voters carefully throughout presidential contests, and we know it well. Having no true party alliance, independents can drift into either side's camp and thereby elect the president.

The fact that such a large percentage of these voters are willing to support something as drastic as the impeachment of the president and vice president tells me that the depth of the irritation with the president over his handling of the war, and over his political tin ear when (not) listening to the public's rising discontent, is becoming a powerful political force in itself.

Having been close to former Speaker Newt Gingrich when his Republican-majority House of Representatives pushed for the impeachment of a president, I can vouch that pursuit of impeachment can be tricky enough to backfire on those who initiate it.

That's why I don't expect current Democratic Speaker Nancy Pelosi of California to allow the nascent impeachment movement to grow much larger.

Nevertheless, the astounding public sentiment expressed in this poll illustrates just how far Bush and Cheney may have set their party back.