The top Republican presidential contenders hold their fourth debate Tuesday in Milwaukee, Wisconsin, amid shifting poll numbers and increasing attacks on each other. This debate will feature the top eight candidates based on a minimum standing of at least 2.5 percent in the latest polls.
Rubio and Cruz rising
Bush's slide in the polls has created an opening for other establishment contenders, according to Republican strategist Ford O'Connell.
"I think that Jeb Bush was the person they thought was mostly likely to do it,” O'Connell said. “But now the jury is out on Jeb Bush and it is giving a real opportunity to Florida Senator Marco Rubio and Ohio Governor John Kasich."