With six months to go until the election, it’s still too early to judge whether Robert F. Kennedy Jr., the Democrat-turned-independent candidate for president, will prove to be more than a mere spoiler.

He starts out with roughly 10 percent of the vote and one of the most famous names in American politics. It’s enough to at least contemplate whether he’ll be the kind of third-party candidate who makes a lasting mark.

Even without having won the presidency, third-party candidates have often played an important and even healthy role in American politics.

They can elevate new issues, represent marginal constituencies and sometimes even win plenty of votes: Six third-party candidates have either won states or reached double digits in the national vote since the rise of the two-party system. They can be a lot more than mere spoilers.

The polling shows many of the conditions for a successful third-party candidacy could be in place. Voters dislike both candidates. They’ve been dissatisfied with the state of the country for 20 years, but for the most part the campaign season hasn’t been focused on solutions to customary longstanding problems. It’s enough to wonder whether this might be the first time since 1992 that a third-party-candidate gains a meaningful foothold.