What must happen before a third party can be considered a legitmate party?

i need to see the answer to answer the question

                the united states presidential election of 1912 was the 32nd quadrennial presidential election, held on tuesday, november 5, 1912. the election was a rare four-way contest.

                incumbent president william howard taft was renominated by the republican party with the support of its conservative wing. after former president theodore roosevelt failed to receive the republican nomination, he called his own convention and created the progressive party (nicknamed the "bull moose party"). it nominated roosevelt and ran candidates for other offices in major states. democrat woodrow wilson was finally nominated on the 46th ballot of a contentious convention, to the support of william jennings bryan, the three-time democratic presidential candidate who still had a large and loyal following in 1912. eugene v. debs, running for a fourth time, was the nominee of the socialist party of america.

                wilson won the election, gaining a large majority in the electoral college and winning 42% of the popular vote, while roosevelt won 27%, taft 23% and debs 6%. wilson became the only elected president from the democratic party between 1892 and 1932, and the second of only two democrats to be elected president between 1860 and 1932. this was the last election in which a candidate who was not a republican or democrat came second in either the popular vote or the electoral college, and the first election in which all 48 states of the contiguous united states participated.

hope this !

-austint1414