Two public choice theories of fiscal policy: 

Under Starve the Beast, the spenders tell the tax-cutters, “If you get what you want, that means I can’t get what I want.”  It’s a story of limits to budgets, limits to borrowing, limits limits limits. 

Under the alternative view, which I call the Ant and the Grasshopper, the spenders tell the tax cutters, “If you get what you want, then I’m definitely going to get what I want.”  It’s a story of childish pettiness, childish tantrums gone awry, childishness childishness childishness. 
Both channels are surely at work.  But in modern American politics, I think all sides are quite good at ignoring limits.