Democrats pounced on the opportunity as Mourdock made a series of quick missteps that alarmed more moderate Republicans. In a series of interviews the day after his primary victory, Mourdock said compromise should consist of Democrats bowing to Republican demands and stood by tea party views popular with the most conservative voters, but not many others.
"To me the highlight of politics, frankly, is to inflict my opinion on someone else," he told MSNBC the day after the primary.
Mourdock later tried to tack back toward the middle with declarations that he could work with Democrats, but he stumbled again in a televised Oct. 23 debate when he explained his opposition to abortion except in cases in which the mother's life is in danger.
"I struggled with it myself for a long time, but I came to realize that life is that gift from God. And, I think, even when life begins in that horrible situation of rape, that it is something that God intended to happen," Mourdock said.
Republicans, including presidential nominee Mitt Romney, initially distanced themselves from Mourdock but later walked their criticism back, with many saying they didn't agree with his statement but supported Mourdock's candidacy.
Democrats spent millions of dollars flooding the airwaves with those comments and other statements by Mourdock in a bid to attract disillusioned Lugar supporters.
Mike Murphy, a former Republican state lawmaker and veteran operative, cautioned that Mourdock's loss should not be read as a repudiation of the tea party, but one man's incredible efforts to wrench defeat from the jaws of victory.
"What happened with Mourdock was personal self-destruction, it wasn't a complete repudiation of conservative ideas in the Republican Party," he said.
Exit polling showed Indiana voters picking the economy as their top issue, driving victories for other Republicans. But it also showed women breaking heavily for Donnelly.