In a Tight Presidential Race, Third-Party Candidates Present a Wild Card

With a month to go before what is widely expected to be an extraordinarily close election, an extra element of unpredictability looms: In every battleground state, there is at least one third-party or independent presidential candidate on the ballot. None of these candidates will come anywhere close to winning the presidency. Jill Stein, the Green Party nominee, is polling at about 1 percent nationally, according to New York Times polling released last week. Same with Chase Oliver, the Libertarian Party candidate. But their presence on the ballot in just a...