This month's Senate elections in Georgia — yes, it was barely two weeks ago — qualified as life-changing news for President-elect Joe Biden, who knew that if the chamber remained in Republican hands his ambitious agenda would be brought to a standstill.
But Biden still faces an obstacle — and it's still the hard-to-control U.S. Senate.
Republicans no longer have a majority, and in the 50-50 Senate, Vice President-to-be Kamala Harris will be able to cast tiebreaking votes. But don't expect harmony.
Democrats are a fractious lot, and expecting them to walk lockstep is like expecting Donald Trump to apologize: It's not going to happen.
Democratic leader Chuck Schumer of New York will run the place instead of Republican leader Mitch McConnell of Kentucky, and the two men are already discussing a bipartisan agreement on committee budgets and procedures. It will probably be called a "power-sharing deal," but that will be an overstatement. Schumer will control the agenda.
That doesn't mean, however, that the minority leader won't try to gum up the works — and in a Senate this close, he'll have power to do so.
"There's no guarantee that Chuck Schumer will get anything done if he doesn't get the cooperation of Mitch McConnell," former Democratic leader Tom Daschle told me.
On some issues, Schumer should have little problem. With 50 votes plus Harris, Biden's cabinet nominations should be easy to confirm fairly quickly; judicial nominations, too.
With 50 votes, Democrats will also be able to pass a budget bill, through the process known as reconciliation. They'll do their best to pack the measure with anything that can be described as budgetary: an economic stimulus package, a modest expansion of Obamacare, tax hikes on the wealthy.
But most of Biden's other priorities will need 60 votes to move ahead. That includes a new Voting Rights Act, immigration reform and a $15 minimum wage.
And he'll still face McConnell, the implacable obstructionist who battled then-President Barack Obama to a standstill in 2009 when Democrats held a much larger, purportedly "filibuster-proof" majority of 60 seats.
Back then, McConnell spurned Obama's appeals to compromise and made sure other Republicans did too. He believed his party's route to power lay in opposing the Democratic president at every turn.
And he succeeded. Republicans won a majority in the House in 2010, a majority in the Senate in 2014 and the White House in 2016.
So there's every reason to expect McConnell to try the same gambit again.
But two elements are different now.
A 50-50 Senate is inherently unstable. It gives every senator a chance to create an instant majority by voting with the other side.
If Joe Manchin of West Virginia, who calls himself a conservative Democrat, refuses to vote for a bill he considers too expensive, most of his home state voters will applaud.
Manchin isn't the only wild card. Individual senators love the idea of individual senators holding the balance of power. A dozen relative moderates have been waiting for this moment: Democrats like Jon Tester of Montana and Kyrsten Sinema of Arizona, Republicans like Mitt Romney of Utah and Lisa Murkowski of Alaska.
"There are a lot of senators on both sides who are frustrated," Angus King, the independent senator from Maine, told me. "We go through hell to get here, and then we don't get anything done."
Then there's the Biden factor. The new president campaigned as a champion of bipartisan horse-trading. He claimed that his 36 years in the Senate gave him the fingertip skills and personal touch to make Congress work. He even promised, famously, that his election would move Republicans toward "an epiphany," a moment of revelation when they would abandon their partisan ways.
Now he has not only a chance but a duty to try to make that campaign promise come true. After Jan. 20, senators expect to get plenty of invitations to the White House — more than most saw from either Trump or Obama.
One more effect, perhaps the most important: A 50-50 Senate will pull Biden and his agenda toward the center. He can't risk losing the votes of moderates like Manchin, Tester or Sinema. And, being Biden, he'll be tempted to try his luck in wooing a few Republicans over to his side, disrupting McConnell's inevitable attempts at obstruction.
On those budgetary issues that can win with only 50 votes — an economic stimulus package and tax hikes — he may be able to satisfy his party's liberal core. But on health care, climate change and other priorities, progressive Democrats are likely to feel frustrated, abandoned, even betrayed.
Especially since, as they will no doubt remind their new president, they hold a majority — remember?