Donald Trump is in a pickle. It doesn’t seem to matter what he does or doesn’t do. According to 538’s national polling average tracker, the former president’s share of the electorate was at 43.5 percent on the day Joe Biden dropped out of the running. Today, in his race against Kamala Harris, his share of the vote is 43.5 percent. All the new movement, as the pollsters say, has been on the Democratic side. To put this another way, the vice president is the fluid candidate. She can move voters, with good performances and bad. Trump, however, is the static candidate. He can’t move voters at all …