US President Joe Biden on Wednesday hailed a "good day for democracy" after a surprisingly strong performance in midterm elections, with Republicans inching toward a slim majority in only one chamber of Congress.

Biden, while acknowledging voters' frustration, said that an "overwhelming majority" of Americans supported his economic agenda and indicated he was leaning toward seeking a second term in 2024, although he said he would make a decision early next year.

The incumbent party historically loses in midterm elections and Republicans had hoped for a major sweep after hammering Biden over stubbornly high inflation, with many also backing unfounded claims over the legitimacy of his defeat of Donald Trump two years ago.

"It was a good day I think for democracy. And I think it was a good day for America," Biden told a White House news conference.

"While the press and the pundits were predicting a giant red wave, it didn't happen."

It was also an underwhelming night for Donald Trump, who was counting on a big Republican showing to boost another White House run.

"While in certain ways yesterday's election was somewhat disappointing, from my personal standpoint it was a very big victory -- 219 WINS and 16 Losses," Trump said in a reference to candidates he personally endorsed.

In addition to seeing several of his high-profile candidates lose, Trump also saw his main rival for the Republican presidential nomination in 2024, Ron DeSantis, notch up a thumping victory to remain governor of Florida.

Republicans appear to be on track to reclaim the 435-member House for the first time since 2018, but by a mere handful of seats.

"It is clear that we are going to take the House back," said top Republican Kevin McCarthy, who hopes to be the chamber's next speaker and who put on a brave face after his party fell short of picking up the 60 seats he once predicted.

For his part, Biden pointed out in a tweet that -- while the count in some places was still ongoing -- his party "lost fewer seats in the House of Representatives than any Democratic president's first midterm election in at least 40 years."

- 'Clear and unmistakable message' -

An election drubbing would have surely raised questions on whether Biden should run again in 2024. But instead he did better than his two Democratic predecessors, Barack Obama or Bill Clinton, who both took a hammering in their first midterms.

Asked about his plans at Wednesday's press conference, Biden said it was still his "intention to run again" -- but that he would decide for sure "early next year."

America's oldest-ever president, who turns 80 this month, Biden hailed the "historic numbers" of young people who voted and pointed to support for the right to abortion, which was rescinded in June by a Supreme Court transformed by Trump appointees.

"Voters spoke clearly about their concerns," Biden said. "There's still a lot of people hurting."

"They sent a clear and unmistakable message that they want to preserve our democracy and protect the right to choose in this country."

Biden, who served for 36 years in the Senate, also struck a more conciliatory tone with the Republicans, saying he would work with them and that the "vast majority" were "decent, honorable people."

With three key races yet to be called after Tuesday's vote, the Senate remained in play but it was leaning Democratic and control may hinge on a runoff election in the southern state of Georgia in December.

While the night saw wins by more than 100 Republicans embracing Trump's "Big Lie" that Biden stole the 2020 election, several hand-picked acolytes of the former president came up short.

"Many of the candidates he endorsed underperformed and cost their party a chance at picking up seats that should have been winnable," said Jon Rogowski, a political science professor at the University of Chicago.

"Not only did voters reject many of Trump's candidates, but they also rejected his policies," Rogowski said, citing abortion as an example.

In ballot initiatives in five states, voters supported abortion rights in a rejection of the conservative-dominated Supreme Court's ruling in June that overturned a constitutional right to the procedure.

Republicans needed just one extra seat to wrest control of the evenly divided Senate.

But by Wednesday the only seat to change hands went to the Democrats, with John Fetterman, a champion of progressive economic policies, triumphing in Pennsylvania over Trump-endorsed celebrity doctor Mehmet Oz.

A Republican-held House could still derail Biden's agenda, launching investigations, scuttling his ambitions on climate change and scrutinizing the billions of US dollars to help Ukraine fight Russia.

Wisconsin's incumbent Republican Senator Ron Johnson was declared the winner on Wednesday, but counting the remaining votes in Senate races in Arizona and Nevada could take days.

Georgia is to hold a runoff on December 6 after neither candidate crossed the 50 percent threshold needed for victory in the Senate race there.

Republican blowback at Trump after limited election gains

Donald Trump was hoping to surf a Republican "red wave" to a fresh White House bid, but with only limited gains in Tuesday's midterm elections -- and an outstanding result for his chief intraparty rival -- the former US president seems to be left out to sea.

Though Republicans look likely to wrest control from the Democratic Party in at least one chamber of Congress, projections show they will not gain the large number of seats typical when the sitting president's approval ratings are so low, and inflation so high.

In the House, early results suggested Republicans were on track for a majority -- but only by a handful of seats -- while control of the Senate remains on a knife-edge and may hinge on a runoff election in the southern state of Georgia in early December.

Trump, who has teased the potential launch of a presidential campaign on November 15, remained in the spotlight throughout the campaign -- putting his thumb on key Republican primaries and holding rallies nationwide, during which he repeated his baseless claims of fraud in the 2020 race.

But with several of his hand-picked candidates underperforming -- some even losing Republican-held seats to Democrats -- analysts and some in his party are blaming him for the party's underwhelming election night.

Meanwhile, Florida Governor Ron DeSantis, who has barely hidden his intent to run for president in 2024, resoundingly won reelection, cementing the rising Republican star's position as a formidable Trump opponent.

The day after the polls newspapers hailed DeSantis' rise, while Republican voters in Scottsdale, Arizona compared him favorably to Trump.

"Trump, he's just about his ego," small business owner Lisa Christopher, 60, told AFP. "DeSantis knows when to push and when to back off and Trump doesn't."

Retired crane worker Bob Nolan said Trump had "too much baggage."

"He was who we needed. But I think ... DeSantis is more down to earth and ready to run."

University of Chicago's Jon Rogowski told AFP that it should have been easy for Republicans to take back the House and the Senate by "a wide margin," pointing to the negative economic environment and Biden's low approval ratings.

"Many of the candidates he (Trump) endorsed underperformed and cost their party a chance at picking up seats that should have been winnable," said the political scientist.

"Other Republican candidates with whom he'd feuded publicly won their seats easily."

- Candidate 'quality' -

The midterm results show that "you can be a conservative, you can be principled, you can oppose Trump -- and win," Peter Loge, a media professor at George Washington University, tells AFP.

Geoff Duncan, Georgia's lieutenant governor and longtime critic of the former president, told CNN Wednesday morning: "I think Donald Trump's moving from a movement to a distraction for the Republican Party."

Before the election on Tuesday, lead Senate Republican Mitch McConnell had voiced concern over the "quality" of some Trump-backed candidates.

In Pennsylvania, Democrats were able to flip a highly-prized US Senate seat with constant attacks on the Republican candidate, celebrity doctor Mehmet Oz, who had never held public office before and lived mostly in New Jersey.

The Republican candidate for Pennsylvania's gubernatorial race, the right-wing and anti-abortion Doug Mastriano, who was present at the January 6th assault on the US Capitol, also lost.

Some notable exceptions, however: the Trump-backed candidate for the US Senate seat from Ohio won, as did more than 100 Republican candidates who challenged the 2020 presidential election results, according to US media projections.

Biden hails 'good day for democracy' as Republicans fall short in elections

Trump on Wednesday morning was "livid" and "screaming at everyone," according to CNN reporter Jim Acosta, citing an adviser to the former president.

While he admitted that the election results were "somewhat disappointing," Trump on Wednesday posted to his Truth Social page that "from my personal standpoint it was a very big victory," pointing to the likely Republican win in the House.

Rogowski says he expects Trump "will be eager to move past 2022 and will declare his candidacy for 2024 sooner than later."

Some political commentators have speculated Trump might delay his November 15 announcement, but he has not yet revealed any change in plans.

Another of his possible 2024 rivals -- his former vice president Mike Pence -- will publish his memoirs that same day.

A preview of those memoirs appeared in the Wall Street Journal Wednesday, with Pence recounting the pressure Trump laid on him to overturn the 2020 election results.

Such an early campaign launch by Trump, just under two years from the actual election, would serve to "consolidate his support early and crowd out other potential candidates," says Rogowski.

"But if he felt he were in a strong position, he would not need to declare so early."

While some may be hoping Trump steps aside and lets candidates such as DeSantis pick up the Republican banner, Loge says that is highly unlikely.

"The problem of becoming the next Trump is that the current Trump has to leave the stage," he says.

"Donald Trump isn't very good at leaving the stage."