When you mention that his race is very winnable, you touch on an important point.
A lot of people either don't have, or take the time to research the candidates and their chances of winning.
If the candidates were a little more interactive with the DP, by letting us know their numbers, or some of their strategy, or simply why they think they can beat their opponent, they might have better results as far as fund raising.
I will check Amash out, and seriously consider it.
I made a substantial donation this month already for a service member riding in a Multiple Sclerosis fund raiser, and have tapped my extra income for the month.