This chart, from a paper by political scientists Matt Grossmann and David A. Hopkins, shows that governance usually means bigger government, even when Republicans are in charge.
The cleanest way to shrink the size of government is to repeal laws and regulations. But it doesn't happen very often. In the American political system, Grossmann says, "it's hard to pass anything, but it's particularly hard to repeal a law that already exists." Systematic analyses show it's rare for laws to be repealed wholesale. "That creates perpetual disappointment among the Republican base," Grossmann continues.
As such, gridlock is often the best small-government conservatives can hope for. And so they're more comfortable with it than Democrats.
Major policy changes tend to be liberal — and that was even true in the Reagan era
The chart above codes significant policy changes by whether they expand or contract the "scope of government regulation, funding, or responsibility." Policy changes turned out to be more than three times as likely to expand the scope of government as to contract it. This is often true even when Republicans are signing the laws.
President George W. Bush is a good example. He passed a series of tax cuts which conservatives mostly liked. But his other major domestic accomplishments — No Child Left Behind and Medicare Part D — sharply expanded the role of the federal government in education and health care, and today they're used as evidence that Bush wasn't really a conservative president.
Political scientists find that's led to a real difference between the two parties
In the paper, Grossmann and Hopkins look at data from Pew Research Center polls that asked Democrats and Republicans whether they prefer politicians who stick to their principles or politicians who compromise. This is a clever way of testing voters' interest in passing policy, as the American political system famously requires compromise to get anything done.
Democrats consistently prefer politicians who compromise and Republicans consistently prefer politicians who stick to their principles.
Part of this is because it turns out to be easier for the government to do new things than to undo old things
The paper is a reminder that American politics is fundamentally rational. Republicans are uncompromising because compromise tends to expand the scope of government. Democrats are willing to make deep concessions because policy moves in a generally liberal direction.