US President Barack Obama has urged senior Republicans to formally withdraw their endorsement of Donald Trump as their presidential candidate.At a rally in support of Democratic contender Hillary Clinton, Mr Obama said it didn’t make sense to denounce Mr Trump’s controversial remarks while still backing him for the White House.Many top Republicans have distanced themselves from Mr Trump over a video in which he boasts of groping women, reports BBC. Mr Trump accused them of disloyalty.He was particularly scathing about House Speaker Paul Ryan whom he described as a ‘weak and ineffective’ leader.Addressing a campaign rally in Greensboro, North Carolina, on Tuesday evening, Mr Obama questioned how senior Republican politicians could still want Mr Trump to be president.‘The fact is that now you’ve got people saying: ‘We strongly disagree, we really disapprove... but we’re still endorsing him.’ They still think he should be president, that doesn’t make sense to me,’ he told the crowd.Mr Obama said Mr Trump’s crude comments about women would disqualify him from even working in a shop.‘Now you find a situation in which the guy says stuff that nobody would find tolerable if they were applying for a job at 7-Eleven,’ he said.Mr Obama was interrupted several times by anti-Clinton campaigners but seemed unfazed, saying: ‘This is democracy at work. This is great,’ The hecklers were escorted from the venue by security officials.