Donald Trump was due to stage a rally in Alabama on Saturday night, in a city that has declared a Covid emergency and in support of a congressman who both backed Trump’s attempt to overturn the election and this week sympathised with a man who threatened to blow up the US Capitol.

The former president will speak in Cullman, Alabama, in part in support of Mo Brooks’ bid to swap his place in the US House for a Senate seat.

Like other southern, Republican-run states, Alabama is struggling with a surge in cases of Covid-19 fueled by the contagious Delta variant. On Thursday, the city of Cullman declared a state of emergency.

“We want to prevent as many non-Covid related things as possible, so our hospital can use its resources to focus on the pandemic and its variants,” said Luke Satterfield, an attorney for the city, according to AL.com. “We don’t want to put any extra strain on them.”

In a statement on Saturday, Trump said he expected a “huge crowd and tremendous enthusiasm” as there was “much to discuss, mostly having to do with bringing our country back”. Local media reported that organisers expected about 40,000 to attend at York Farms. The former president was set to take the stage at 7pm local time.

Dr William Smith, chief medical officer for Cullman Regional, told CBS42: “We view this as a potential ‘super-spreader’ event, just like last week’s Rock the South [at the same location]. We’ve seen an increase in patients since that event last weekend and we’re concerned we could see the same impact.”

Trump’s presence will also put strain on Brooks’ opponents in the Republican race to fill the Senate seat being vacated by the retirement of Richard Shelby.

In 2017 Republicans experienced defeat in Alabama when Judge Roy Moore lost to the Democrat Doug Jones amid allegations of sexual misconduct involving underage girls which he denied. But Jones was beaten in 2020 and the state remains solidly Republican.

Brooks has been a leading backer of Trump’s attempts to overturn his clear election defeat by Joe Biden, joining the president in speaking at a “Stop the Steal” rally near the White House before Trump supporters attacked the US Capitol on 6 January.

This week, Brooks caused widespread anger in Washington with a statement in response to a standoff near the Capitol between police and a man who said he had a bomb.

Floyd Ray Roseberry, 49 and from North Carolina, broadcast on Facebook during his standoff with police, expressing anti-government grievances. Arrested and charged with threatening to use a weapon of mass destruction and attempting to use an explosive device, he could face life in prison.

Appearing before a federal judge in Washington on Friday, Roseberry said he had not taken his “mind medication”. He was ordered to undergo a mental competency hearing.

On Thursday, Brooks said he was praying for police and first responders but also tweeted: “Although this terrorist’s motivation is not yet publicly known … generally speaking, I understand citizenry anger directed at dictatorial Socialism and its threat to liberty, freedom and the very fabric of American society.

“The way to stop Socialism’s march is for patriotic Americans to fight back in the 2022 and 2024 election. I strongly encourage patriotic Americans to do exactly that, more so than ever before. Bluntly stated, America’s future is at risk.”

The statement was widely condemned. Adam Kinzinger, a Republican from Illinois who broke with party leaders to join the committee investigating the Capitol attack, said Brooks’ words were “evil”.

The Republican party, Kinzinger said, “has a decision to make. Are we going to be the party that keeps stoking sympathy for domestic terrorists and pushes out truth, or finally take a stand for truth. I’ve made my decision, so has Mo. Now it’s up to GOP conference leadership to make theirs.”