Donald Trump and his Republican allies have levied consistent attacks against President Joe Biden based on his age, but they are now less than enthusiastic after Biden dropped from the race and endorsed Kamala Harris, according to a GOP strategist. Biden earlier on Sunday released a statement saying he would “stand down” from his campaign, and instead choose to focus on finishing out what’s left of his term in office. He later endorsed Harris, which led to a swell of donations that one observer called “off the charts.” But Trump and Republicans who focused for years on Hunter Biden’s laptop mi…