[AuH2ORepublican]

True, but he was defeated in the lrimary. Let me rephrase: who was the last Senator to be defeated in the general election after having won unopposed the prior time?

[fieldmarshaldj]

I'm reviewing several states, but it's quite possible the answer is "none" (at least in the popular vote era). Aside from some Southern states that didn't contest prior to the 1960s, virtually every Senate race has had some sort of opposition candidate. Technically, Pryor wasn't really unopposed, as he faced a Green Party challenger (whom I'm sure some Republicans, nevermind disgruntled leftists, cast a protest vote for). Still, Lugar and Pryor facing no opponent from the main opposition party is highly unusual, regardless.

However, in 2008, AR's GOP was utterly decimated, leaving John Boozman as the sole statewide (federal or state) figure, and he probably figured it would be ill-advised to make a run that year. Still, though, we should've run a state legislator who could've softened Pryor up.

Conversely, I think there was a tactical reason why the IN Dems didn't field a candidate against Lugar in '06, choosing instead to focus on targeting GOP House seats. Without a strongly-contested Senate race, there wasn't a whole lot of reasons for Republicans to turn out en masse (well, except for House races). It worked, as they knocked off 3 of ours, grabbing a majority of the House delegation for the first time since 1992 (and it took us 6 more years to reclaim those 3 seats, but only to lose Lugar's).

[fieldmarshaldj]

Well, just reviewed all the Senate races as fast as possible, and the answer to your query (with respect to the popular vote era), and that is that no Senator unopposed in a prior election has lost in a general at the next.