How can a strong third-party candidate impact the two-party system in the united states?

A strong third-party candidate can upend the traditional two-party system in a number of ways.

The most important is that it will likely draw candidates from one of the candidates from the two major parties.

This means that a third-party candidate, in the United States, is unlikely to win and is more likely to be seen as a "spoiler" candidate for one of the two major party candidates.

This was seen with Ralph Nader in the 2000 election and Ross Perot in the 1992 election.

Third party candidates can also upend the discussion as it will force the two major party candidates to fight (and pander for the votes that the third party candidate is attracting.