For historical context, here's the link to the Wiki of popular vote history:

The leading third party candidate in the last three elections has been the Libertarian candidate:

2020 - Jo Jorgensen (0 Electoral Votes, 1.87m Popular Votes, cc 1.12%)

2016 - Gary "What is Aleppo" Johnson (0 Electoral Votes, 4.49m Popular Votes, cc 3.28%)

2012 - Gary "Before What Is Aleppo" Johnson (0 Electoral Votes, 1.28m Popular Votes, cc 0.99%)

With approximately 240 million eligible voters in the US as of the 2020 election, a third party candidate would need, at approximately 60% turnout, 2.9 million votes to achieve a 2% share of the popular vote.

Resolves YES for any non-Republican, non-Democrat candidate in the 2024 US General Election for President receiving 2% or higher of final popular vote total. Will not resolve until Inauguration Day 2025

Edited note: This market does not round up. The minimum must be a percentage of 0.02 or higher.