THE Republicans' apparent dissatisfaction with their primary candidates has led some people to wonder whether there might be room for a third party in this year's presidential race. Gary Johnson, the former governor of New Mexico, obviously thinks so: he announced last week that he will run as a Libertarian. Ron Paul supporters wonder whether the congressman from Texas might make an independent bid, assuming he can't win the Republican primary. Americans Elect have gathered more than 2.3m signatures in their quest to put up an unspecified non-partisan candidate. Donald Trump might be on the ballot in Texas. None of these efforts threaten to succeed. As Rand Paul noted when asked about his dad's chances, such a run would only boost Barack Obama's chances of re-election. It's becoming clear, however, that a lot of Americans aren't excited about the available options.

And while we can identify a lot of subgroups who aren't particularly thrilled with Mr Obama or any of the Republican frontrunners, I suspect the biggest untapped constituency is people who are fiscally conservative and socially moderate or liberal. These are people who could be described as classical liberals, or libertarian, or liberaltarian, but probably aren't describing themselves that way, because none of those labels are in widespread usage outside of heavily politicised circles, and all of them have political baggage. As it is, they're not going to be a good fit with either party. Suppose, for example, you're a young woman who wants to cut federal spending (as 71% of women between 18 and 29 do, according to a September poll from Generation Opportunity) but also supports marriage equality (as 59% of that age cohort does, according to the Pew Research Center). Who are you going to vote for?

So I was interested in this piece by my colleague, guest-blogging at Bleeding Heart Libertarians. The unruly independent nature that drove my colleague to engage with libertarianism in the first place is perhaps summarised by the title of the post, "Why I'm Not a Bleeding-Heart Libertarian". He explains that he holds a number of beliefs that break with libertarian orthodoxy: taxation "is often necessary and legitimate", for example, and the distributive consequences of certain legal rights is relevant to the justification of those rights. "Given the prevailing public understanding of 'libertarianism'", he writes, "I'm no libertarian. And it's not at all clear to me what is to be gained by trying to get people to retrofit the label to fit my idiosyncratic politics."

But Timothy B. Lee, of the libertarian Cato Institute, isn't having it. He notes that libertarians are dealing with a double standard:

American liberalism and American conservatism are sprawling political coalitions bound together by a cluster of shared values, assumptions, and associations. If your politics are closer to Ted Kennedy than Ronald Reagan, then you're a liberal, and vice versa for conservatives. In contrast, libertarianism tends to be defined much more narrowly. It's often defined as the belief that the government should be limited to a night watchman state: police, courts, military, and nothing else. And there's an anarchist wing of the libertarian movement that thinks even these functions can and should be provided by the competitive market.

Mr Lee notes that he has his lapses too, but he still considers himself a libertarian, because he trends toward the libertarian side of the spectrum on most policy issues. And he argues that my colleague is also a libertarian, despite what he says about it.

I'm not sure whether Mr Lee is right, but I feel that he should be. The double standard he identifies is real, and constrains the viability of the libertarian message—and it is perpetuated by the Libertarian Party, if not by "libertarians" more broadly construed. The Libertarian Party of Texas, for example, which picks its nominees at convention rather than through a primary, asks potential candidates to assert doctrinal soundness: "I have read the Libertarian Party of Texas platform...and I understand the planks. Unless identified below, I will not deviate from these principles while campaigning." (See page 14 of the candidate handbook.) That's significantly more stringent than either the Republicans or Democrats; both of the major parties try to enforce the party line through various methods—pledges, primaries, etc—but remain somewhat heterogeneous, or at least encompass several subsets of voters.

In being so rigorous about ideological purity, libertarians aren't doing themselves any favours. There are currently no Libertarian (Party) members of Congress, although there are some who identify as libertarian, including Mr Paul, who is from Texas and is a Republican. And as my colleague's post makes clear, they're effectively alienating people who would be effective advocates for certain libertarian values. Under most circumstances, voluntary organisations are allowed to set their own standards for inclusion, so the Libertarian Party can continue this way if they want to. But principles and beliefs aren't property, so Mr Lee (or my colleague) should be free to identify as libertarian. And given how many Americans seem to fall outside the going political binary, with the fiscal and social conservatives yoked together, somewhat artificially, against the economic and social progressives, this would be a propitious moment for libertarians, or classical liberals, to build a bigger tent.