Congressional Republicans lodged a formal case Monday for the impeachment of US President Joe Biden, using the opening day of the Democratic National Convention to launch a political assault unlikely to gain serious traction. The report from three powerful committees in the Republican-led House of Representatives accuses Biden of corruption linked to his son Hunter’s foreign business affairs. Jim Jordan, head of the Judiciary committee, said the probe showed “conclusively” that Biden had “abused his public office for the private financial benefit of the Biden family and Biden business associates.” However, Republicans have not provided any direct proof that Biden ever used his office to benefit his son or was involved in Hunter’s businesses. There was no smoking gun in a document built around inferences and innuendo about connections between father and son, with many of the accusations related to the period when Biden was out of office, after serving as Barack Obama’s vice president. Biden — set to deliver a swan song speech at the Democratic convention and pass the political torch to his vice president Kamala Harris — has repeatedly denied helping his son’s business ventures.