Sometimes in politics, you lose when you think you've won. That may have happened to Indiana Republicans this week.
In their primary they defeated their incumbent, thirty-year veteran Richard Lugar in favor of a new challenger, state treasurer Richard Mourdock, whom the Washington Post describes as a "staunch" conservative. I don't know; is there any other kind? In any case, it seems reasonable that Lugar attracted moderates of all parties, independents etc, who may be skeptical of the more right-wing Mourdock. Mourdock won statewide office twice but that was before the Tea Party joined the Republicans, perhaps driving some of the GOP into the ranks of the Dems.
You can still project an election this fall in which the Republicans win the Senate, but it's not as easy as it was before Lugar lost. He was a good candidate and a good senator. Mourdock? We'll find out.