The Democrats have secured control of the United States Senate, giving Joe Biden a mid-term boost as he heads into the final two years of his first term as president.
With one seat still in doubt, the Democrats claimed a majority on Sunday when Nevada senator Catherine Cortez Masto was re-elected, defeating Republican challenger Adam Laxalt.
The party now has 50 seats in the 100-seat Senate, with the newly elected Senate to be sworn in on January 3, 2023.
While control of the US House of Representatives is still to be decided, and a run-off election will take place to decide who claims one of Georgia's Senate seats, the Democrats have retained a Senate majority by virtue of Vice-President Kamala Harris's tie-breaking vote.
Speaking to reporters after AP declared Ms Cortez Masto as winner of the Nevada Senate seat, Mr Biden said he felt good about the election results.
"I'm looking forward to the next couple of years," he said.
So, what does a simple senate majority mean for the rest of Mr Biden's term?
Result to impact judicial appointments
Even though Democrats are unlikely to control the House, a simple majority in the Senate will give the party the ability to approve judges picked by Mr Biden to fill positions on district courts, circuit courts and high courts.
This will be particularly crucial to Democrats if a seat on the US Supreme Court, which now has a 6-3 conservative majority, opens up in the final years of Mr Biden's term.
When the outgoing US Senate returns this week, Majority Leader Chuck Schumer aims to immediately confirm two more federal judges, awaiting final votes.
Win gives Democrats more legislative control
House Republicans, if they pull out a victory, have pledged to try to roll back Mr Biden's victories on battling climate change and want to make permanent a series of 2017 tax cuts that will expire.
But by claiming control of the Senate, Democrats can reject legislation sent over by a possible Republican-controlled house.
The Democrat majority will also ensure a smoother process for Mr Biden's cabinet appointments.
Budget resolutions will also pass easier as they only require a simple majority to pass.
However, even if the Democrats do win the house, they will be short of the 60 Senate votes needed to move many kinds of major legislative changes.
Republican plans for Biden investigations shelved
Republicans have planned investigations into the activities of the Biden administration and the president's son, Hunter, who has had business dealings with Ukraine and China.
But by retaining a simple Senate majority, Democrats will keep control over committees and investigations, as well as blocking any attempts by a Republican house to impeach Mr Biden.
Biden says claiming control of house a 'stretch'
It was still unknown which party will hold the majority in the 435-seat US House of Representatives for the next two years, with multiple seats yet to be called by AP.
It could take several days or more before the outcome of enough house races are known to declare which party has a majority.
Most recently, Democrats scored a significant upset with a projected victory in Washington's third congressional district, where Democrat Marie Gluesenkamp Perez defeated Joe Kent, a candidate endorsed by Donald Trump.
And returns are still flowing in for several races, including many in liberal-leaning California.
But Republicans continue to have an edge on winning control of the house.
On Sunday, Mr Biden said the prospect of his party keeping control of the House was "a stretch".
Biden optimistic about Georgia
Mr Biden was more positive about the party's prospects in Georgia, where a run-off election between Democrat incumbent senator Raphael Warnock and Republican football star Herschel Walker will take place.
The run-off will be held on December 6 to decide who wins the seat, after neither candidate secured at least 51 per cent of the vote, as required by state law.
A win in Georgia would expand the Democrats' majority to 51-49.
That, in turn, would give Democrats an additional edge in passing a limited number of controversial bills that are allowed to advance with a simple majority of votes.
With 51 Democratic seats, the influence of Democratic senators Joe Manchin and Kyrsten Sinema would be slightly diluted.
Both Senator Manchin and Senator Sinema have blocked or delayed some of Mr Biden's major initiatives, including expansions of some social programs.
Mr Biden said on Sunday he was confident of winning that extra-seat buffer.
"We're focusing now on Georgia. We feel good about where we are. And I know I'm a cockeyed optimist. I understand that," Mr Biden said.
Republicans in battle to claim Alaska
The winner of one other Senate seat is also up for grabs.
But the fate of the Alaska Senate seat will not have an effect on Senate control as it is already known which party will claim the seat.
Kelly Tshibaka was slightly leading fellow Republican and incumbent senator Lisa Murkoski on Sunday, with about 20 per cent of the vote still to be counted.
ABC/wires
