President Trump was headlining a rally in Minneapolis on Thursday evening, even after his campaign threatened a lawsuit over the city’s effort to recover $530,000 in security costs relating to the event The rally, Trump’s first since the House moved toward impeachment over his handling of a July phone call with Ukraine’s president, is in a state Trump nearly won in 2016 and has talked frequently of capturing in 2020 But it takes place in a traditionally liberal city and the home turf of a frequent foil, Democratic Rep Ilhan Omar. Local news reports indicated that scores of Trump supporters — as well as pro-impeachment demonstrators — lined up hours before the event at the Target Center in downtown Minneapolis began At the rally, Trump said more than 20,000 people were inside the arena — and more than 25,000 were outside, out of nearly 100,000 who indicated online that they wanted to attend The dispute over the rally’s security costs erupted late Monday when the campaign accused Mayor Jacob Frey, a Trump critic, of trying to sink the rally Frey called the costs reasonable and said he had a duty to protect taxpayers. The campaign said the city sent the security cost estimate to Target Center’s operator, AEG Management, which threatened to cancel its contract to host the rally if the costs weren’t covered Its law firm threatened to sue AEG if the rally doesn’t proceed. Trump attacked Frey Tuesday on Twitter, writing: “Someone please tell the Radical Left Mayor of Minneapolis that he can’t price out Free Speech Probably illegal!” His campaign said the “bogus security charges” are an attempt to prevent Minneapolis residents from supporting Trump, and contrasted them with what they said were much smaller charges for a 2009 event by then-President Barack Obama in the same building “The radical leftist mayor of Minneapolis, Jacob Frey, is abusing the power of his office and attempting to extort President Trump’s re-election campaign,” Trump’s campaign said in a statement LEGAL EXPERTS WEIGH IN AS WHITE HOUSE OBJECTS TO INQUIRY When the rally was announced last month, Frey said Trump’s “message of hatred” would never be welcome in Minnesota But, at a news conference Tuesday, he said the city will do all it can to guarantee a “safe and peaceful week,” regardless of his political differences with Trump Frey stood by the security-cost estimate, saying a Trump political rally would bring “significant expenses” not associated with Obama’s 2009 event, which was aimed at building support for health-care reform Later Tuesday, the Trump campaign said in a statement that the operators of Target Center had backed off canceling the contract, with no agreement by the campaign to pay additional money AEG didn’t respond to messages seeking comment. Trump also attacked Frey over Twitter for a policy prohibiting city police officers from wearing their uniforms in support of candidates at political events or in campaign ads A spokesman for the city’s police union has complained about the policy, and the union has been selling “Cops for Trump” T-shirts CLICK HERE TO GET THE FOX NEWS APP Frey said the police force must be nonpartisan and non-ideological “They’re free to express their First Amendment rights but should do so off-duty,” he said Fox News’ Chad Pergram and The Associated Press contributed to this report.