Seriously,

Use our own money.

Crowd-source I suppose if people want to feel like they are a part of something but encourage only very small donations. 

Promise to only serve one or two terms, depending on whats accomplished the first term. 

Not taking anyone's (PAC's special-interest group etc) money, 

and not caring about re-election?

To whom would I be beholden to?

God, you and me and my conscious.

Just flat out tell the other Senators:

 "I didn't come here to get  rich, I already am, 

I didn't come here to get re-elected, 

I've got better things than that planned for my future. 

But I did come here to raise nine kinds of Holy-hell with you sons of bitches 

and fight for what's right 

and I plan on doing it with everything I got."

We're gonna have such a great time Lucy :-).