Which is difficult due to the many barriers put in by the two major parties to getting on the ballot. Many third parties spend a lot of their funds just trying to get on the ballot and defending against law suits put out by major party candidates. Leaves very little for campaigning or advertisement, relying almost solely on word of mouth and volunteers. And of course each state runs their own elections, so there is never a one size fits all solution. Plus, the rules are constantly changing and generally becoming more difficult.