Dan Bishop, the conservative Republican, has won the special election for US congress in North Carolina’s ninth district.

The 55-year-old state senator is best known for a law dictating which public toilets transgender people can use.

He was strongly backed by Donald Trump, who staged a raucous election-eve rally for him, during which he pushed unfounded allegations about voter fraud and launched a false attack on Democratic candidate Dan McCready.

The president railed against his opponents, claiming falsely that they were not “believers in religion”, and that they hated America and had helped mass “illegal voting” take place in California.

Mr Bishop’s narrow victory was a boost for Mr Trump’s Republicans, who lost their House majority in the 2018 midterms. But the sub-5,000-vote-winning margin reported by NPR, or 50.8 per cent to 48.6 per cent, came in a district the GOP had held for some six decades.

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Mr Bishop thanked Mr Trump and vowed to support the president’s agenda in Washington. He said his victory should send a message nationwide that voters were rejecting the “radical, liberal policies being pushed by today’s Democratic Party”.

Mr Trump attempted to take credit for the win, tweeting: “Dan Bishop was down 17 points 3 weeks ago. He then asked me for help, we changed his strategy together, and he ran a great race.”

But no polling has emerged publicly that showed Mr Bishop with a deficit that big. Operatives from both parties and analysts had previously described the race as too close to call.

The win was a high point in a difficult few days for the president, who fired his national security adviser John Bolton after Afghanistan peace talks collapsed – Mr Bolton maintains he resigned – and a new opinion poll suggested his ratings were slipping amid fears of an economic recession.

The North Carolina result underscored the rural-urban split between the parties, with Mr Bishop running up substantial numbers in outlying areas and Mr McCready eroding GOP advantages in suburban regions.

The Democrat’s moderate profile resembled that of many of his colleagues who won in Republican-leaning districts in the 2018 midterms in a “blue wave” that stripped Mr Trump’s party of its House majority.

Mr Bishop’s margin was far less than the 11 percentage points by which Mr Trump captured the district in 2016. And it was only slightly greater than when then-GOP candidate Mark Harris seemed to win the seat over Mr McCready, 36, last year – before those results were annulled due to evidence of vote tampering.

Republicans have held the seat since 1963, and its loss would have been a worrisome preface to the party’s presidential and congressional campaigns next year.

“I think it means Trump is going to get a second term, and Republicans will retake the majority,” House minority leader Kevin McCarthy said. Many analysts think a GOP takeover will be difficult.

A second Republican, Greg Murphy, also won a House seat on Tuesday in North Carolina’s third congressional district.