Hoosiers aren't big Democrats, they tolerate them in small doses, and are very conservative. Indiana Republicans had a rough primary season, and a no vote from Donnelly would only further unify opposition to the one-term Democrat. He voted for Gorsuch, and can hardly afford to mobilize pro-Trump Hoosiers. Donnelly could pay with out of state liberals who bankroll him if he votes yes, so he's in quite a pickle. Odds are, he votes for Kavanaugh.