Republicans, Democrats, and the White House have all reached separate decision points for 2010—and possibly for 2012, as well.

Republicans had assumed they were harnessing the energy of the Tea Party movement. Instead, with the ABC/Washington Post poll now registering majority disapproval of the Tea Party, Republicans find themselves in an accelerating march of folly. As a result, they have diminished their moment and will capture fewer seats in 2010.

In Nevada, Democratic Majority Leader Harry Reid saw his strongest potential opponent impale herself on the far right’s opposition to health reform, proposing to “repeal and replace” it with a barter system of chickens for medical care. Instead, Republicans nominated Sharron Angle, who sounded less weird than Chicken Lady but who is, in fact, decidedly more extreme—determined to dismantle Social Security, Medicare, and the Department of Education just for starters. Angle’s now whitewashing all that from her website, but Reid will hold her to it—and likely hold his Senate seat, which should have fallen to Republicans.

Obama confronts a tipping point for his presidency. But it has nothing to do with the oil spill.

From Kentucky, where Senate nominee Rand Paul has pushed the GOP over the ideological edge, to California, where GOP voters pushed their newly minted nominee Carly Fiorina onto an ideological outcropping from which she almost certainly can’t defeat Democrat Barbara Boxer, the party is squandering its best chances for November. The march of folly now reaches Florida: HMO executive Rick Scott, whose company was involved in massive Medicare fraud, has outflanked Attorney General Bill McCollum, leading McCollum by 13 points in the Republican gubernatorial contest. And former Republican, now Independent, Charlie Crist, the incumbent governor who committed the mortal sin of standing, literally, with Barack Obama to rescue Florida’s economy, has sustained a lead over both Democratic contenders and the GOP’s Tea-infused Marco Rubio.

The potent brew that Republicans were counting on may prove to be political hemlock instead. Do they dare put down the tainted chalice?

Democrats, too, must choose. For the midterms and beyond they must decide whether to run with Barack Obama or away from him. In Arkansas, Sen. Blanche Lincoln was almost universally pronounced the next incumbent casualty before the votes were counted Tuesday. After she prevailed, one Democratic “insider” refused to let the conventional wisdom die, saying she survived because the electorate wasn’t “anti-incumbent” but “anti-establishment.” But Lincoln was rescued by ads touting Obama’s support (after she’d abandoned him on health reform) and by a barnstorming Bill Clinton. You don’t get more establishment than that.

It’s hard to understand why congressional Democrats, with their parlous poll ratings, would distance themselves from Obama, whose favorable rating is 52 percent in the ABC/Washington Post survey. There may be a few districts where candidates can stand or fall on local issues; most Democrats this year will stand or fall with the president.

Obama himself confronts two challenges—and one of them could be the tipping point for his presidency.

It isn’t the BP oil spill. Despite a gathering consensus among the press and the political community, and continued bad news pouring out of the Gulf, moving from the glib notion that this is Obama’s Katrina to the ahistorical suggestion that this is Obama’s Iran hostage crisis only confirms that the oil spill, like Obama, is sui generis.

Americans know that Obama can’t stop the oil by threatening to bomb Tehran—or the leaking well. Indeed, before the crisis is over, he may turn it to the purpose of reviving and passing an energy bill that combines conservation and investment in alternatives with new safeguards for drilling.

Obama’s real danger—and it was Carter’s true weakness in 1980 as well—is a faltering economy. The recovery could stall or plunge into a double-dip recession. That’s why the anemic job numbers for May drove the Dow down, and had to dismay even the most optimistic White House aides.

The remedy is not entirely within the president’s control.

The U.S. economy was in a steady, if job-stingy, upturn until the financial turmoil in Greece spread across the euro zone. This blow to the financial sector and stock prices has been compounded by ideological decisions in Germany and Britain to slash spending at precisely the wrong time. The combination has depressed prospects for all but anemic growth across one of the world’s largest markets. In Britain, the latest estimate is that unemployment will now rise to nearly 3 million—the grim toll under the last Conservative government—and remain nearly that high until 2015. The London Times reports that in the public sector alone “725,000 jobs … face the ax.”

Abruptly applying the fiscal brakes in Europe is loony economics. In this globalized world, its impact will be felt from Baltimore to Dubuque to San Diego. Obama could counter with a bigger jobs bill or a second stimulus. But passing either has been made more daunting, if not impossible, in part because the President didn’t convince Americans of the sometime-utility of deficits when he had their undivided attention last year. Obama chose the course of least resistance —a muted defense of spending now, fiscal restraint later. That may be the right policy, but the rhetoric left too many voters believing, in defiance of history and economics, that the solution to a downturn is a balanced budget.

Obama was elected to end the recession, so falling back into it would be a fundamental threat to his re-election. In 1982, Reagan confronted deepening economic difficulties, and his approval ultimately fell to 35 percent, far lower than Obama’s is now. Obama’s task today is tougher than Reagan’s then. But the test is the same—to “stay the course.”

The president and his party will have to stand together to survive the midterms and to triumph in 2012. They will be aided by Republican folly—but that won’t be enough to save them. This is a tipping point—a moment to seize or be seized by events. During his 2008 campaign and the great legislative clashes of the last two years, Obama has shown a remarkable capacity to tip events in his favor—and in a progressive direction. Now he has to do it again.