The fate of the US Senate remained in the balance Sunday night as Republicans inched closer to capturing a majority in the House, a day after Democrats surpassed forecasts and historical norms in midterm elections.

Thousands of ballots remained to be counted in the Nevada and Arizona Senate races, in which Democratic incumbents were attempting to fend off Republican challengers. The races had not yet been called.

Edison Research predicted neither Democratic incumbent Raphael Warnock nor Republican Herschel Walker would reach the 50pc threshold necessary to avoid a December 6 rematch. If the parties split those races, the fate of the Senate would hinge on a Georgia runoff election for the second time in two years.

Edison Research predicted that the Republicans gained at least ten seats in the House of Representatives. That would be three more than the number needed to seize control of the chamber from the Democrats, albeit with 42 contests remaining undeclared, the Democrats still had a slim chance of retaining the majority.

Even with a narrow House majority, Republicans would be able to impede Democratic President Joe Biden's remaining two years in office by obstructing legislation and initiating potentially politically damaging investigations.

Mr. Biden, speaking at a White House press conference, vowed to engage with Republicans and defended his administration's first two years as a result of the surprisingly strong Democratic performance.

Mr. Biden stated, "The American people have made it clear that they want Republicans to be willing to work with me as well."

In addition, he reaffirmed his intention to run for re-election in 2024 but stated he would make a definitive choice early in the following year.

Republicans failed to achieve the sweeping "red wave" win they had hoped for, but Democrats avoided the kind of devastating midterm defeat that frequently plagued sitting presidents.

The findings indicated that voters punished Mr. Biden for presiding over an economy afflicted by sharp inflation, as well as Republican efforts to prohibit abortion and the nation's vote-counting procedure.

Poor performances by some candidates favored by Donald Trump, notably Walker, suggested tiredness with the type of disruption fomented by the former Republican president, casting doubt on the sustainability of his potential 2024 presidential bid.

Mr. Biden portrayed Tuesday's election as a test of American democracy as hundreds of Republican candidates accepted Mr. Trump's phony allegations that the 2020 presidential election was stolen from him.

On Tuesday, several election skeptics who supported Mr. Trump's accusations were voted to office, while a majority of those seeking posts to oversee state elections were defeated.

Mr. Biden stated, "Our democracy has been tested in recent years, but the American people have spoken with their votes."

Fears of violence or disturbance at polling booths by far-right observers were unfounded.

The director of the US Cybersecurity and Infrastructure Security Agency, Jen Easterly, stated that she found no evidence that any voting system had been corrupted.

With control of the Senate, Republicans would be able to oppose Mr. Biden's judicial and administrative nominees.

John Fetterman, however, flipped a Republican-held US Senate seat in Pennsylvania, defeating Trump-backed celebrity physician Mehmet Oz and boosting his party's hopes of retaining the upper house.