A new poll of likely Iowa caucusgoers shows Ben Carson vaulting to the top of the Republican field to tie with Donald Trump. A Monmouth University poll released Monday shows Carson and Trump each with 23 percent support. “This marks the first time since July 26 that a poll in any of the first four nominating states has not shown Trump with a nominal lead,” a Monmouth author reports. Carson’s 15 percentage-point gain comes as Wisconsin Gov. Scott Walker dropped 15 since July.