Lugar has been one of the “sainted ones” for so long, his campaigning skills have atrophied.
He, like so many other entrenched senators, is simply unused to having to go fight for his job.
You’ve nailed it. Lugar has coasted for so many years that he’s forgotten how to campaign. He’s also surrounded by a senior staff who have been with him for 20-plus years. That, btw, speaks well of him as a senator and a boss; he’s a gentleman, not one of the jerks. As he’s aged, he’s also burrowed more and more into the Foreign Relations Committee, which is fine except that it does nothing for him politically.
George Bush should probably have made him Secretary of State and let someone a generation younger take the seat.