Mark Penn, who has been a pollster and consultant to the presidential campaigns of Bill and Hillary Clinton, John Anderson, and Ross Perot, writes about political discontent in Britain and the United States in the Washington Post today, noting that in this country

socially liberal and fiscally conservative voters believe, especially after what happened with health care, that they have no clear choice: They must sign on with the religious right or the economic left.

Exactly the point that David Kirby and I have been making in our studies on the libertarian vote, as in the first line of this January study:

Libertarian — or fiscally conservative, socially liberal — voters are often torn between their aversions to the Republicans’ social conservatism and the Democrats’ fiscal irresponsibility.

Libertarian-leaning voters are a large swing vote, and they do indeed find problems with both parties. As parties increasingly cater to their “base,” libertarian-leaning independents find themselves dissatisfied with both liberal Democrats and conservative Republicans. We noted in our first study, “The Libertarian Vote,” that according to the 2004 exit polls, “28 million Bush voters support[ed] either marriage or civil unions for same-sex couples” and “17 million Kerry voters … thought government should not … ‘do more to solve problems.’ ” That was 45 million voters who didn’t seem to fit neatly into the red-blue, liberal-conservative dichotomy.

But Penn is on less solid ground in his next line:

It is just a matter of time before they demand their own movement or party.

Movement, maybe. The Ron Paul campaign certainly appealed to antiwar, small-government voters. And the Tea Party movement focuses almost exclusively on economic and constitutional issues, making it more appealing to libertarians than typical conservative organizations. Meanwhile, as the Tea Party opposition to the Democrats’ big-government opposition surges, so does progress toward marriage equality and rational drug reform. Maybe those various libertarian-leaning groups will find each other. But a new party is a much bigger challenge. It’s no accident that the only third party that achieved even modest success in recent history was headed a billionaire who was also a celebrity, Ross Perot. Ballot access laws, campaign finance restrictions, exclusion of third-party candidates from debates and media coverage, single-member districts — all make it difficult to start a successful third party. It may also be the case that moderates, who tend not to be very angry, and libertarians, who don’t really much like politics, are particularly ill suited to undertake the massive amount of work that a new party requires.

But Penn is absolutely right to point to the plight of “socially liberal and fiscally conservative voters,” forced in every election to “sign on with the religious right or the economic left.”