Republican Governor Terry Branstad, a 5 termer, leads presumptive opponent, Democratic State Senator Jack Hatch 43-38 with 12% undecided. However, when informed of the Governor's new scandals that range from secret secret agreements and reparations with fired state employees to the firing of a police officer who clocked the Governor's SUV for speeding, Branstad leads Hatch only 41-40 with 19% undecided.A few other things to, Branstad's approval which sat above 50% before is now at a negative 43-45 approval (not good considering that's below 44). Branstad is still doing very well among his Republican base, but Hatch is now winning Indies by 15. Most voters are aware of the scandal, they think Branstad does know somewhat about the scandal and they think an independent counsel should be hired by the legislature (likely to happen in the IA Senate), but they don't think he should resign.
Unfortunately, Hatch is a flawed candidate and lacks youth, money, name ID, and is a very urbanized, liberal Senator so it's going to be hard for him to win a lot of the rural and younger voters who are tired of Branstad. The race leans R now, but not before he fends off a primary challenger and requires money to go into his own race that would have ultimately gone into the Senate race. Like South Carolina, this is probably Branstad's race to lose.
Here's a recent, good article on the race, to (though they use the Suffolk Branstad +10 poll which was also conducted after the scandal).