A new US Congress has assembled, and the Republican Party now has a majority in both the House of Representatives and the Senate.
That's a gift to president-elect Donald Trump, who will need the support of Congress to fully implement his MAGA agenda.
But the tight numbers present challenges for Trump in both chambers.
In the Senate, his plans face being stonewalled by the much-maligned "filibuster".
And in the House of Representatives, a few rebel Republicans have already defied Trump, albeit briefly, in their first vote.
The vote for a leader
The first task for the House of Representatives was electing a speaker to run House business.
Republican Mike Johnson held the job in the previous Congress, and he had Trump's backing to continue.
"A win for Mike today will be a big win for the Republican Party," Trump posted ahead of the vote.
But during the initial round of voting, several Republicans refused to support Johnson.
Thomas Massie, Ralph Norman and Keith Self voted for another Republican member instead.
Another six Republicans, all members of the far right House Freedom Caucus, refused to respond when they were called on to vote.
Those six Republicans ended up submitting late votes for Johnson, but it wasn't enough to give him a majority. The House appeared on track for a second round of voting.
It prompted some huddling with colleagues and a phone call with Trump, and Norman and Self agreed to change their votes.
That gave Johnson the speakership — after highlighting how the Republicans' House majority could still throw up some hurdles for Trump.
[tweet: chip roy]The House
In the November election, the Republicans won 220 seats, and the Democrats won 215.
That gave Republicans the "smallest margin of control in modern history", according to the Pew Research Centre.
And that margin of control has shrunk further. Republican congressman Matt Gaetz quit Congress with (failed) hopes of becoming attorney-general. Fellow Republicans Elise Stefanik and Mike Waltz are also vacating their seats to take up Trump administration roles.
That will reduce the Republican majority to 217-215, meaning one defector would be enough to kill a bill.
[datawrapper: house]Special elections to replace Mr Gaetz and Mr Waltz have been scheduled for April 1. An election date for Ms Stefanik's seat has not been set. They're all in safe Republican districts.
"We're assured to have Republicans re-elected in all these seats," Republican House leader Mike Johnson told Fox News after Trump announced the appointments.
"And we'll work with a smaller majority of one or two for the amount of time that we have to."
The Senate
Thirty-four of the Senate's 100 seats were up for grabs in November. Republicans took four of them from Democrats, giving them a 53-45 majority.
[datawrapper: senate]There are also two independents, who generally side with the Democrats, so the split is more like 53-47.
JD Vance, as the new vice-president, will take tie-breaking vote powers from the outgoing vice-president, Kamala Harris.
Trump's likely roadblock
To get legislation through the Senate, it's not enough to have a simple majority of the votes.
That's because of a rule known as a the "filibuster".
It means a bill can only be put to a vote if 60 (out of 100) senators agree that debate on the bill should end, and the bill should progress to a vote.
If it falls short of this "supermajority" support, the bill won't be put to a vote at all. (Once a bill is put to a vote, it only needs a "simple majority" of 51 votes to pass it.)
So, when the majority party has fewer than 60 people in the Senate, it relies on the support of senators from the other party to progress a bill.
In other words, the party that lost the election can still block the winning party from putting any new law to a vote.
Since the Republican Party will only have 53 senators, passing any legislation will require at least seven Democrats to agree that it should be put to a vote.
"So it's not like the Democrats are dead or on life support — they still have a tremendous amount of power, especially in the Senate," says political scientist Todd Belt from George Washington University.
"It's going to be very difficult and very delicate for Donald Trump — who is not known for his delicacy in terms of trying to get some legislation passed."
Trump has other options to progress his agenda — such as by issuing executive orders, which give presidents the power to make policy without Congress. The Trump team is understood to have a pile of these prepared in advance, to be signed off on day one.
But there are limits to the powers of executive orders. A policy that requires new funding, for example, generally needs the support of Congress.
'The clock is ticking'
Trump has been elected president for a four-year term, but Republican control of Congress may not last that long.
"The clock is ticking for Donald Trump, and the reason why is because incumbent presidents usually lose members of the House and Senate in the very first midterm election," Professor Belt says.
"With the margins being so close in both chambers, it looks like Donald Trump doesn't have four years to establish a legacy. He probably only has two years, at least a legislative legacy.
"He can do things in foreign policy, and he can do things with executive orders, but those, as we have seen, are short term and can be very quickly undone by his successor."
