The victor needs at least 35 percent.Still, 16 percent of likely Republican primary voters remain undecided in the 11th hour, and almost three in four say they could be persuaded to vote for someone else.he is a lot of room, potentially, for things to shake a little, said J. Ann Selzer, who conducts the Iowa Poll for the Register.A bad sign for Jacobs: His numbers dropped through four days of p