The war in Afghanistan is shaping up as an important test of whether President Obama craves popularity above all or whether he is willing to make the tough, sometimes unpopular decisions that being commander in chief require. A new Washington Post–ABC News poll finds sharply declining levels of support for the war effort, especially among the president’s Democratic constituency. By 51-47 percent, a majority of those surveyed now find the war “not worth fighting.” That represents a gain of six points for the antiwar side since last month. Only 24 percent believe that troop numbers should be increased, while 45 percent think they should be decreased.

Within those numbers lies a sharp partisan divide. As the Post account notes:

Overall, seven in 10 Democrats say the war has not been worth its costs, and fewer than one in five support an increase in troop levels. Nearly two-thirds of the most committed Democrats now feel “strongly” that the war was not worth fighting. Among moderate and conservative Democrats, a slim majority say the United States is losing in Afghanistan.

Republicans (70 percent say it is worth fighting) and conservatives (58 percent) remain the war’s strongest backers, and the issue provides a rare point of GOP support for Obama’s policies. A narrow majority of conservatives approve of Obama’s handling of the war (52 percent), as do more than four in 10 Republicans (43 percent).

In other words, Democrats are bailing out on the Afghanistan war as they previously bailed out on the Iraq war. Actually, by 2007 even many Republicans were turning against that war. But President Bush ignored the public and surged anyway. That was the best decision of his entire presidency and one that may save his historical reputation despite all the other blunders he committed. Will President Obama have the gumption to be equally steadfast if Gen. Stan McChrystal requests more troops (as is widely rumored)? Who knows? So far he has shown himself to be pretty staunch on Afghanistan, but administration officials such as National Security Adviser Jim Jones and Secretary of Defense Bob Gates seem to be signaling that troop requests would be unwelcome. If they are in fact trying to discourage McChrystal from asking for more resources (and it’s not clear that’s the case), they would be making a grave mistake.

For the Washington Post–ABC News poll confirms that in Afghanistan the same dynamic applies as that which held in Iraq and in most of our other wars: the public is skeptical because they don’t see enough signs of progress. Only 42 percent think we’re winning in Afghanistan, 32 percent think we’re losing, and 22 percent aren’t sure. Fully 62 percent say they are “not confident” that the newly elected Afghan government “can rule the country effectively.”

What this suggests is that if we can regain momentum—if our forces can provide palpable evidence that the war is not only winnable but that we are in fact winning it—then public opinion can be brought back around. And the surest way to achieve the progress the American people rightly expect is to send more troops.

Yes, the number of U.S. troops has already more than doubled over the past year—from 33,000 to 68,000. And, yes, there are 33,000 other troops in Afghanistan from our NATO partners. But Afghanistan is a big country—bigger than Iraq in both area and population—and yet the size of its security forces is less than a third of that in Iraq. Iraq has more than 600,000 security personnel; Afghanistan, fewer than 170,000; and based on current projections, it will take years to substantially increase that number.

That means that for the near term, the bulk of the fighting required to wrest parts of eastern and southern Afghanistan out of Taliban control will have to be done by coalition troops, and specifically by American troops, since most of our allies are unwilling either to fight or to provide the resources for fighting effectively. Only by adequately resourcing the war effort and pursuing an effective counterinsurgency strategy can the U.S. armed forces make the progress necessary to raise public support for the war effort and win what President Obama has just described as a “war of necessity.”