Stating the fact doesn't explain the fact. It isn't some Law of the Natural Order that a congressman can't get elected. There are reasons that appears to be so, but what are those reasons? If we define them, perhaps they can be overcome.
I would think that there are 2 reasons:
1. Usually, being a member of the House is not "notorious enough" to get much name recognition, which is the first pre-requisite to winning the White House.
2. Congressmen (and Senators) have the problem of having voted, at one time or another, for massive omnibus bills with pork packed away in their deep recesses. Before long it will be revealed that Hunter voted for research in left-handedness in Peruvian frogs or studies on the sexual lives of Korean dragonlies or somesuch. This needs to be overcome.
My suggestion is to hit them head on. Duncan looks a tad portly. He can use this as a good-humor asset. He could do a bicycle tour of every district in California to a) LOSE some weight and b) build support in his home state for the convention get some attention. Pick a slogan like "Lose with Duncan Hunter" because then the whole thing will get some attention.
Then he could hit the "what I voted for" head-on with humerous ads of Duncan, flanked by massive thousand-page tax bills. "You wouldn't believe what I've had to vote for....." would be a great theme of those early "getting to know you" ads. It's very important that those first ads be sunny and humerous, the kind that make people say to themselves "tell me more."
If he doesn't do this type of thing, and do it quickly, the MSM will do the defining, and that would be disastrous.
Dude, stay away from any marketing-related careers...LOL