Donald Trump has dared Oprah Winfrey to enter the White House race in 2020, saying he wants her to be “exposed and defeated”. Bringing the curtain down on an active weekend of tweeting, during which he addressed suggestions of collusion with Russia and criticised the FBI, the President declared he had been left unimpressed by the talk show host’s appearance on CBS News programme 60 Minutes. Oprah met 14 voters in Michigan last year – seven who voted for Mr Trump and seven who did not – to discuss how they felt about the President, and they reconvened to mark his first year in office. It was broadcast on Sunday night and Mr Trump tuned in. The talk show host met with voters…