The Troll Master pulls their strings and continues to pull them into his trap.

Quote from article: "Like a master puppeteer, Trump pulls the strings and the Democratic presidential candidates are forced to pivot to any topic he tweets about. He sets their daily talking points – they don’t."

https://www.foxnews.com/opinion/arnon-mishkin-trump-has-set-a-trap-for-his-dem-opponents-and-theyre-falling-for-it