"Seattle mayor contest to swirl around who’s more progressive," the online headline in the Seattle Times says.

The November race between Seattle Mayor Mike McGinn and state Sen. Ed Murray is shaping up as a battle over who’s the more progressive candidate and who’s more effective at advancing a progressive agenda.

It is an interesting frame, and not one that necessarily favors their endorsed candidate. But I think it's a little off. No, this isn't a race between two progressives. It's a race between a progressive and a liberal. So if we're going to define the mayoral race in terms of the two candidates' relative progressivism, the first thing we need to do is define the terms.

Yeah, I know, most people tend to use the words "liberal" and "progressive" interchangeably, and as political ideologies they share a lot in common. For example, when it comes to social issues, there's little that separates Murray and McGinn. But the two words are not synonyms, and the difference largely expresses itself in how the two ideologies attempt to use government to achieve an often shared economic agenda.

American economic liberalism tends to focus on using taxpayer dollars to incentivize and subsidize economic activities and programs perceived to improve the common good. That is the kernel of truth behind the supposedly disparaging term "tax and spend Democrat." But American liberalism, while emphasizing the need to balance individual liberty with social and economic justice, remains deeply rooted in the classical liberalism from which it evolved (that of John Locke, Adam Smith, and John Stuart Mill), and as such remains guided by a profound respect for the supremacy of the market.

Modern American economic progressivism, by comparison, has less ideological baggage, having grown out of the less dogmatic (and thus more incoherent) populist and progressive political movements of the late 19th and early 20th centuries. Progressives tend to take a more expansive view of the role of government in regulating economic activities and in establishing minimum standards. Progressives don't reject markets, but they believe that government has both the authority and the obligation to guide market forces toward social ends, while correcting for the worst instincts of capitalism. It is the collective wisdom of the people as expressed through their democratically elected government that stands supreme, not the collective wisdom of the market.

Or at least, that's how I define the terms. For example, the Earned Income Tax Credit is a liberal policy, whereas the minimum wage is progressive. The Wall Street bailout was grounded in liberalism, whereas a reimposition of the New Deal era Glass–Steagall Act would be progressive. The federal subsidies provided consumers to purchase private insurance policies at the heart of Obamacare is a distinctly liberal policy, whereas the elimination of pre-existing condition exclusions and the imposition of minimal coverage standards are progressive. (A government-run public option would have been even more progressive.)

It can be a subtle distinction because their ends are often the same—and throughout most of the New Deal era, liberalism and progressivism tended to work hand in hand—but liberals prefer to use the market, whereas progressives aren't shy about attempting to constrain or even sidestep it.

Of course, few politicians, let alone voters, self-conciously check off against these definitions when evaluating public policy. And in fact, given the definitions I've provided, most Democrats might consider themselves equally liberal and progressive. But the revival of the progressive label over the past quarter century has not just been a clever attempt at center-left rebranding; it is a reaction to the abandonment of progressive economic values by the Democratic establishment in the face of pro-market, anti-regulatory pressure from the right, and as such represents a very real (if hard to define) schism within the party itself.

In a subsequent post I will argue that, personalities aside, it is this schism that is at the heart of Seattle's mayoral race, and that best defines the ideological differences between Mike McGinn and Ed Murray.