For the third election in a row, American voters have upended their nation's political order. Their deep frustration with an unresponsive system has again led them to recast its central players.
The result is a Congress in which both ends of the political spectrum will be unusually well represented, complicating the delicate task of building consensus just when the country's grim challenges require it most.
"Do we wish to live free, or be enslaved by debt?" Kentucky senator-elect Rand Paul asked as he savoured a landslide win. "Do we believe in the individual, or do we believe in the state?"
Talk like this could lead to gridlock. It will mean bitter tension not only between the parties, but within them. If this Congress proves to be no more effective than the last couple in rebuilding Americans' faith in their central governing institution, Democrats and Republicans could both pay the price next time.
Americans threw Republicans out of the majority in 2006 and finished the job in 2008 by electing a Democrat as president. But two years of one-party rule under Barack Obama have left voters more dissatisfied with the way Washington works than when they embraced his post-partisan promise.
Now, Americans are hoping divided government - with Republicans controlling the House of Representatives, both parties almost evenly matched in the Senate, and Mr. Obama in the White House - will force all of the players to work together to address their country's daunting problems.
A lack of jobs, of course, is the biggest. But a government that grew unsustainably large when it replaced a cratering private sector during the financial crisis is a close second and, in many minds, an obstacle to solving the first.
The historic arrival of a boisterous batch of Tea Partiers in Congress - led by Kentucky's Dr. Paul, the Tea Party's resident intellectual, and Florida senator-elect Marco Rubio, its most charismatic voice - makes it impossible to predict how it will all turn out.
These new Republican recruits made it here despite thumbing their noses at the GOP establishment. They are not about to play by its rules now. Their supporters want dramatic results - spending cuts, repeal of the health-care reform law, wholesale retreat of the state - not incremental change.
For John Boehner, the presumptive next speaker of the House, the task of taming the Tea Partiers within his caucus is difficult because they got to Congress owing little to the party. That makes this GOP sweep very different from the party's 1994 rout, when dozens of Republican recruits made it to Washington as hand-chosen disciples of Newt Gingrich.
"These Tea Party people have no loyalty to Mr. Boehner and they are more extreme than the Republican freshmen were in 1994," said James Pfiffner, a public policy professor at George Mason University in Fairfax, Va. "The challenge will be to keep the [GOP]coalition together."
This Tea Party-driven win is also riddled with risk for the Republican Party as it turns in coming months to choosing a presidential nominee to confront Mr. Obama in 2012. The GOP establishment fears that Sarah Palin will use her star power with Tea Partiers in Congress - many of whom won with the help of her endorsement - to corner the nomination.
Washington is feeding on rumours that GOP elites are already plotting to block Ms. Palin's way. But just as establishment choices fell one by one to Tea Party challengers in Republican primaries this year, anybody-but-Palin machinations could backfire.
"There isn't going to be a candidate around who can unify all factions of the party," University of New Hampshire political science professor Dante Scala offered. "For all the talk from the Republican elite about unifying, I wonder if it's already too late."
For Democrats, this midterm election is more than a mere rebuke. It fundamentally reshapes its ranks. With far fewer conservative Democrats returning to Congress, urban progressives will dominate the caucus. They will insist that Mr. Obama press on with an activist government agenda.
They will be challenged by Democrats from outside Congress, most notably by groups such as Third Way. It is pushing for the Democratic Party to move to the centre to capitalize on the GOP's rightward shift. Indeed, Mr. Obama's re-election may depend on it.
"The President may go the Bill Clinton route to build up his centrist credentials," Prof. Scala said. "A lot of [progressive]House Democrats will be put in cold storage for a couple of years."
Americans seem to be asking as much from the President by rendering a compelling verdict on Tuesday night. But even if he is willing to give it a shot, there is no guarantee the Republican leadership will risk compromising with Mr. Obama. Its marching orders may now come from the Tea Party.
The U.S. two-party system is both "structurally and culturally" well entrenched, Prof. Pfiffner noted. But it has occasionally been unable to withstand pressure from within for change. It happened a century ago when Theodore Roosevelt's Progressive caucus broke from the Republican Party, costing the GOP Congress and the White House in 1912.
The GOP has two years to prevent history from repeating itself in 2012.