Democratic consultants are not above recruiting Libertarians to run in swing districts, hoping those candidates will shave away enough conservative votes to keep a Republican from winning. Republicans play, too, hoping Green candidates will whittle away liberal voters who would otherwise support Democrats.

However they get into the races, their effect is undeniable.

Libertarians often get 3 percent of the vote or less in races where both major parties have a candidate. Sometimes, even that slim result is influential.

State Representative Donna Howard, Democrat of Austin, won re-election in 2010 by a dozen votes, getting 48.5 percent of the vote. Ben Easton, a Libertarian, got 2.9 percent, presumably from conservatives who didn’t vote for Dan Neil, a Republican. It doesn’t always go the Democrats’ way: Representative Paul Workman, Republican of Austin, beat an incumbent Democrat in a race where, because of a Libertarian candidate, nobody got 50 percent.

When only a Republican is running, the Libertarians do even better. Bob Townsend got 18 percent in his race against United States Representative John Culberson, Republican of Houston, in 2010. David Sparks got 18.4 percent against United States Representative Kenny Marchant, Republican of Carrollton, in that same election. Greens don’t do as well, but they have done well enough to keep their right to get on the ballot without petitions. Edward Lindsay got 6.3 percent against Comptroller Susan Combs, a Republican, in 2010; Mary Ruwart, a Libertarian, claimed 10.5 percent in that race.

The outsider parties don’t hold primaries, choosing their candidates in state conventions — both on the second weekend in June this year. It’s old-fashioned politics. You won’t see any commercials for these people, probably, in the way the Republicans and Democrats seize your television before a primary. But it’s competitive. The Libertarians meeting in Fort Worth will be choosing from among six candidates for United States Senate. The Greens have two in that race.

Sometimes, the minor parties outdo the major parties. Both of the little parties have candidates for each of two Railroad Commission seats on the statewide ballot. That’s the agency that regulates oil and gas in Texas, no small thing. Texas Democrats fielded only one candidate in one race and nobody in the other.

The small fries haven’t won one yet. But you can’t win if you don’t play.