The heated contest between Herbert and Johnson has already helped drive higher voter turnout in Tuesday's primary election than the 2014 contest.
By Monday morning, voters who had sent in mail-in or absentee ballots that put turnout at nearly 15 percent. Utah's 2014 primary election, where only a handful of legislative races and county offices were on the ballot, saw less than 13-percent voter participation.
Herbert, who became Utah's governor at the height of the Great Recession, is pointing to the state's now-humming economy and low unemployment as he makes his case for another term.
Johnson, the board chairman of Overstock.com, has touted his private-sector experience and criticized the governor's approval of fuel, sales and property taxes over the years.
