For the last 25 years, Republican presidents abetted by Republican congressmen have vastly increased budget deficits, interrupted by 8 years of Democratic control that turned the situation around.
"Conservative" and "conservationist" both have their roots in "conserve": to keep in a sound or safe state. I think it's very clear that "fiscal conservationist" better describes someone trying to stop budget deficits than "fiscal conservative".
I'm a conservationist: one who advocates "conservation," which is "a careful preservation and protection of something." I'm now a fiscal conservationist, as is anyone else who tries to fight massive deficit spending. If the Republicans clean up their act and keep it clean for the next 25 years, we can revisit the issue, but the word choice is clear right now.
P.S. Thought I'd invented the term "fiscal conservationist", but I guess not.
keywords: politics, budget, Lakoff