Grassley is going to win, but the margin will be underwhelming.
Agreed. As I said the other day, the age factor seems to be weighing him down, and the sexual assault allegation against Franken seems to have had little impact. This race is very reminiscent of Strom Thurmond's last reelection in 1996, when he underperformed due to similar concerns over his age.
I think it's less that Grassley is old and more that he chaired the judiciary and was involved in the shepherding of Kavanaugh, ACB, and other controversial judicial nominees. He's always been conservative, but he hadn't been viewed as such a partisan figure before then.