Now that Thanksgiving is over, we're all watching to see whether a certain American leader can extricate himself from crisis and rebuild his popularity...but enough about Tiger Woods. Lest we forget, the president of the United States also has a big task ahead of him. Here is my Sunday print column, updated and expanded:

Barack Obama is poised tomorrow night to expand America's military commitment in Afghanistan, a troop hike decision that is likely to enrage his liberal Democratic base. This strikes me as a problem that could seriously undermine his presidency.

In terms of domestic politics, the first task of any chief executive is to secure the support of his own followers; this is especially true if he's waging a war. A president needs to know that the voters who elected him are on board for the long haul. George W. Bush enjoyed that luxury. Six years ago, he went into Iraq to thunderous applause from his conservative Republican base - which stuck with him for years, long after it became clear that he had hyped the rationale for invasion and failed to win the peace.

By contrast, Obama's imminent dispatch of roughly 30,000 new troops to Afghanistan comes at a time when roughly two-thirds of all Democrats are telling pollsters that the war is not worth fighting; indeed, 57 percent reportedly favor troop withdrawals. The antiwar liberals who propelled Obama's nascent candidacy are worried that an expanded, costly war will wind up sinking his domestic agenda. Democratic strategists are worried that if the war continues to go badly even with the hike in troops (a distinct possibility), liberals might register their disgust by skipping the 2010 congressional elections, thus trimming or imperiling the Democratic majorities on Capitol Hill.

Looming over this week's troop hike rollout is the specter of Lyndon Johnson. Back in 1965, when LBJ launched the first major escalation of U.S. involvement in Vietnam, he enjoyed broad national support (that August, only 24 percent of Americans told pollsters that the war was a mistake), and landslide loyalty from congressional Democrats. But by the winter of 1968, his ambitious domestic agenda was in tatters and the party was torn apart from within.

The Democrats who lit Obama's fuse in the early primaries did so because they assumed he was generally opposed to military adventurism. It's true that he talked up Afghanistan as the right war, but his followers were mostly galvanized by his indictment of Iraq as the wrong war. In that very distant era - two years ago - few rank-and-file Democrats were focused on Afghanistan at all. They had no problems with Obama talking tough about Afghanistan, because they saw it as a political necessity. They knew he'd never get elected unless he exuded some national security gravitas.

But now the deal is real. The irony for Obama is that, in the absence of broad Democratic support, his decision to expand the war will be applauded primarily by the Republicans; nationwide, 60 percent of Republicans are telling pollsters that the war is worth fighting. GOP leaders will probably praise Obama for giving Gen. Stanley McChrystal most of what he wanted, and they'll be glad that Obama has vowed anew to "finish the job," even though nobody really has a clue what a finished job would actually look like.

As we know, however, these people are not Obama's friends. Six months from now, if his benchmarks for success come up short, or if he starts talking about exit strategies (known, in the new parlance, as "off ramps"), they'll quickly try to morph him into Jimmy Carter and deride him as a wimp incapable of command. Granted, Bush was the president who invaded the wrong country after 9/11 (with the GOP's acquiescence) and put Afghanistan on the back burner (with the GOP's acquiescence), thus bequeathing Obama a festering mess with few cleanup options - but, hey, that's politics.

All the more reason why Obama needs strong support from his own party. Certainly, some Democrats do support the troop hike as essential to our national security. Last Wednesday, on a Washington blog, a counterterrorism analyst named Jim Arkedis urged his fellow Democrats to fall into line: "The president will need his party’s understanding and support to succeed. If Democrats fall out over Afghanistan, he won’t be able to sustain a coherent policy, and the public will likely lose confidence in the party’s ability to manage the nation’s security."

But that's a very tough sell. The majority Democratic stance was articulated yesterday by Paul Kirk, the Massachusetts senator who temporarily occupies the Ted Kennedy seat. Writing in the Boston Globe, Kirk said, "We should not send a single additional dollar in aid or add a single American serviceman or woman" unless the corrupt Afghan government gets its act together. Until that happens, Kirk said, "we need not enlarge our military footprint in Afghanistan and risk even more violence for our perceived 'occupation.'"

As far as Senate-speak goes, that's strong stuff; away from the Hill,, other antiwar Democrats are more outspoken. Michael Cohen, a former State Department speechwriter and current Washington think tank scholar, argued in a blog post the other day: "If you want the public to 'lose confidence' in the Democratic party's ability to manage the nation's security, then, yes, mindlessly supporting a strategically dubious war in Afghanistan...is a jolly good idea....I'm getting ready to watch a Democratic president, to whom I've invested a great deal of emotional energy and support, tragically follow this course. But just because the president makes a decision to send more troops into an Afghan quagmire, it most certainly does not mean that his party should blindly follow course."

And his party won't do that. Congressional Democrats are recoiling at the cost of an escalated conflict - Nancy Pelosi remarked the other day that there is "serious unrest in our caucus about can we afford this war" - particularly in the wake of reports that the price tag per soldier is $1 million a year. They don't want to pay for Afghanistan if it means shelving the party's domestic agenda, so some have suggested a solution: a new "war tax" to help finance the wider war.

This idea is being floated by Democratic congressman David Obey, chairman of the House Appropriations Committee. As he argued yesterday on CNN, "If this war is important enough to engage in the long term, it's important enough to pay for," via new taxes, as opposed to simply borrowing more money and fobbing off the debt on future generations. He said that if this war is destined to last another eight to 10 years, "at least you ought to pay for it so that it doesn't destroy every other effort that we need to rebuild our own economy." (By the way, Obey believes that the imminent troop hike is "a fool's errand.")

So...a new tax on recession-burdened Americans? To pay for a war that at this point barely musters 50 percent support in the national polls? That's a synonym for political suicide, and thus not likely to happen. But the fact that a high-ranking Democrat has even proposed such a bill is proof of the party's restiveness. (The pro-war Republicans would never support such a move, of course. They preferred to finance our misadventure in Iraq in part by borrowing heavily from China and sticking our grandkids with the tab.)

The likeliest money scenario, voiced recently by Joint Chiefs of Staff chairman Mike Mullen, is that Obama's escalated war will require a supplemental funding bill next year. Oh, the irony: That's precisely how Bush often did his war business, by circumventing the regular defense budget. During the '08 campaign, Obama won liberal hearts by assailing Bush's budgetary tricks and vowing he'd never finance a war that way. So this too could prompt liberals to cry betrayal.

Obama is surely trying to chart a pragmatic, non-ideological course - signaling that Afghanistan (and, most importantly, its impact on Pakistan) is a vital security interest, while also stressing that the wider war will not be open-ended. Indeed, in his Tuesday night address he is expected to outline his exit strategy goals (if only to reassure his Democratic base), without specifiying how or when those goals may be achieved (thereby unnerving his Democratic base).

All told, Obama will need political strength at home to sustain his mission abroad, and I question whether he can succeed in that effort if most rank-and-file Democrats begin to wonder whatever happened to hope and change.