At his first rally after leaving the White House, former US president Donald Trump on Saturday lambasted the Biden administration's immigration policies and sought to energise Republicans to take back control of Congress next year. Appearing to relish being back in front of thousands of supporters, Mr Trump repeated his false claim that his defeat in the November 2020 election was marred by fraud. Mr Trump left office in the aftermath of the deadly January 6 attack on the US Capitol by his supporters, shortly after a speech in which he urged a crowd to "fight" when Joe Biden's electoral victory was about to be certified by lawmakers. Mr Trump survived a second impeachment on a charge linked to the violence and has managed to retain broad influence over the Republican Party, in part by leaving open the question of whether he will run for office again in 2024. "We won the election twice and it is possible we will have to win it a third time. It is possible," he said. Mr Trump won the 2016 election against former secretary of state Hillary Clinton. He lost in 2020. Whether he runs again could be influenced by the outcome of various legal troubles. The Manhattan district attorney's office has told Mr Trump's lawyers it is considering filing criminal charges against his family business, <em>The New York Times</em> reported on Friday. The former president highlighted parts of his regular grievance list at the rally, with particular focus on the rising number of immigrants crossing over the US southern border, an issue Republicans have zeroed in on to rally their voters. "You have millions of people coming into our country. We have no idea who they are. Joe Biden is doing the exact opposite as we did," Mr Trump said. Mr Biden's White House has called Mr Trump's immigration policies inhumane. While keeping his political plans vague, the former president spoke forcefully in favour of his party taking back control of the US House of Representatives and Senate. "We will take back the House, we will take back the Senate and we will take back America, and we will do it soon," he said. Democrats' razor-thin majorities in both chambers of Congress will be on the line in the 2022 midterm elections and history favours Republicans' chances of gaining seats in those contests. While Trump has made speeches at Republican events since his defeat, the rally in Ohio, a state he won in 2020, marked a return to the freewheeling mass gatherings that have been critical to retaining the support of his enthusiastic base. He campaigned for former White House aide Max Miller, who has launched a primary challenge against Representative Anthony Gonzalez, one of the 10 House Republicans who voted to impeach Mr Trump on a charge of inciting the January 6 attack on the Capitol that left five dead, including a Capitol police officer. Mr Trump has vowed to campaign against all 10. He endorsed a challenger to Senator Lisa Murkowski, the only one of the seven Senate Republicans who voted to convict him in his January impeachment trial who is up for re-election in 2022. The Ohio event in Wellington, about 64 kilometres (40 miles) south-west of Cleveland, will be followed by a trip to the US-Mexico border with Texas Governor Greg Abbott on June 30 and a rally in Sarasota, Florida, on July 3. Supporters said they hope Mr Trump will use such events to help unify the party behind like-minded candidates for Congress. Mr Trump repeatedly attacked what he called "woke generals," after an exchange this week in which the top US military officer hit back against a growing conservative movement opposed to teaching certain theories about racism. "Our generals and our admirals are now focused more on this nonsense than they are on our enemies," Mr Trump said. He criticised the media, a regular foil, and tried to co-opt the phrase "Big Lie", which critics have used to describe his efforts to discredit the 2020 results. Mr Trump's repeated false claims of election fraud have taken hold of Republican voters. About 53 per cent of Republicans believe he won the 2020 election and blame his loss on illegal voting, compared with a quarter of the overall public, a Reuters/Ipsos poll found. Rally attendee Tyler Voyik, 64, said he came to the rally to show his support for Mr Trump, who he voted for in 2016 and 2020. Mr Voyik lives in Ohio but spends a lot of time in Florida. He would support Mr Trump if he received the nomination in 2024 but would prefer Florida Governor Ron DeSantis. "I think he could do better by supporting somebody else, but if he runs I will support him," said Mr Voyik. "If he wins the nomination, I will support him all the way."