This week, the White House sent around a memo titled: “Senator Harry Reid, Then & Now.” It quoted Reid back in November saying: "We're not going to do anything to limit funding or cut off funds" for Iraq. It then quoted Reid a few days ago saying he would co-sponsor a bill to cut off exactly such funding.

The White House’s evident goal here was to highlight Reid’s inconsistency and perhaps even suggest he has broken a solemn promise. But that misses the more salient point: Why has Reid, now Senate majority leader, shifted positions on this key issue?

The likely answer can be found in a press release by Senator Russ Feingold, a Wisconsin Democrat and a co-sponsor of the same bill. “Congress,” he said, “has a responsibility to end a war that is opposed by the American people …” Other opponents of the mission in Iraq have been echoing this talking point as well.

We like to think of our politicians as leaders but most are followers: They do what they think the voters want them to do (that’s the smoothest path to political power), and they divine the will of those voters by reading polls.

Back in November, even after the Democrats bested Republicans in the elections, it was assumed that most Americans would be furious over any attempt to de-fund troops engaged in combat. But recent polls, taken by such organizations as Pew, CNN and the Washington Post suggest that a substantial number of voters no longer see it that way: Confidence in the possibility of salvaging a successful outcome in Iraq is running low; support for Congress legislating a specific date when American troops will come home is running high.

Should politicians come to believe there is less political risk in voting to cut off funds to soldiers on the battlefield than in supporting a war effort led by a low-polling president, many – from both parties – will cast their votes on Capitol Hill to reflect that calculation.

Few will dwell on the likely consequences of such a decision. Among them: The United States – not just President Bush -- will be seen as having been defeated. That will mean more radicalized Muslims, more volunteers for the War on the Free World. Victorious general have no trouble attracting recruits.

Iraq will undoubtedly suffer much more carnage. Those who eventually take power will not be America’s friends. Terrorist groups will make Iraq a base. What will the U.S. do to stop them?

The tactics used to defeat the U.S. in Iraq will be employed in Afghanistan as well. How many bombs will explode in how many markets, schools and police stations before the polls show most Americans ready to leave that corner of the world as well?

And then? The liberal Egyptian writer Tarek Heggy predicts that if the U.S. abandons Iraq to those now dispatching suicide bombers, by 2015 “Morocco, Algeria, Egypt, Sudan, Lebanon, Syria, Jordan, Iraq, Yemen, Iran, Afghanistan & Pakistan (at least) will be in the hands of radical Islamists with at least two nuclear powers among these countries.”

Unimaginable? Sure – just as President Clinton could not imagine that the terrorists who bombed the World Trade Center in 1993 would, within less than a decade, acquire the skills to turn both buildings into rubble; just as President Bush, when he unveiled that “Mission Accomplished” banner four years ago, could not imagine that the Iraq war was only just beginning.

When the U.S. went into Iraq, it was said that failure was not an option. The consequences would be too dire. Today more and more people believe failure is the only option. The consequences be damned.

If we have met our match on the mean streets of Baghdad, there is no reason to delay the inevitable. But there is now a new U.S. commander in Iraq, Gen. David Petraeus. He is pursuing a new and different strategy. It is not just a “surge.”

Retired Gen. Barry McCaffrey, a frequent critic of the Bush administration, recently returned from Iraq. He calls the situation there “grim” but concludes there is a “basis for hope” – indications that Petraeus and his troops may be learning to fight and win a 21st century war.

Because defeat in Iraq would, McCaffrey writes, “imperil U.S. interests for a decade or more,” he urges support “for this one last effort to succeed,” adding that it will take only till the end of summer to determine whether that is possible.

Members of Congress should consider his argument – whatever the polls show.