President Trump's previously resilient base is showing signs of cracking. A new Reuters/IPSOS tracking poll, released Friday afternoon, showed the president with a job approval rating of 75 percent among Republicans. Political professionals generally view it as worrying for any commander-in-chief if his approval ratings with his own party dip below 85 percent - and downright alarming if they go below 80 percent. "Seventy-five [percent] is certainly a new number and I would want to see something that would either back that up or refute it," said GOP pollster David Winston, whose resumé includes work for former Speaker Newt Gingrich...