DES MOINES — GOP gubernatorial challenger Ron Corbett says Kim Reynolds hasn’t shown him much since taking the reins of state government in May from former Gov. Terry Branstad.Corbett, who is stepping down as Cedar Rapids mayor after two terms to take on Reynolds in the 2018 GOP primary next June, said he hoped to see plans to “modernize” Iowa’s income tax system, improve the quality of waterways and address state budget woes during Reynolds’ first 100 days as governor, but none of that has happened.“She didn’t come in as a rookie governor,” said Corbett, noting that Reynolds touted her close working relationship with Branstad as his lieutenant governor.“We need a new game plan for the state of Iowa and, unfortunately, in the governor’s first 100 days, she hasn’t proposed any policy,” he told reporters on the lawn outside the Capitol.