US President Joe Biden tested positive for Covid with mild symptoms Wednesday, shortly after conceding he would consider dropping his re-election bid if doctors diagnosed him with a serious medical condition. The 81-year-old Democrat gave reporters the thumbs up and said “I feel good” as he cut short a trip to Las Vegas and flew to his beach home in Delaware to go into isolation, which will take him off the campaign trail for days. Biden thanked well-wishers on X, adding that “I will be isolating as I recover, and during this time I will continue to work to get the job done for the American pe…