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In 1860, Abraham Lincoln was elected as a 3rd party US presidential candidate.
When Abraham Lincoln ran for office, the two major parties were the Whigs and the Democrats. As a Republican, Lincoln was elected as a third party candidate - even after being left off the ballot in the 11 states that seceded from the Union.

In 1992, for the last time a 3rd party candidate, Ross Perot, was heard in presidential debates.

In 2008, 3rd party’s voices of Bob Barr & Ralph Nader were excluded from debates though
- 55% of likely voters, both Democrat and Republican, said that they would want to see Bob Barr featured in the debates alongside Obama and McCain.
- 59% of independent voters stated that they want to see the debate commission allow Nader into the debates.
- A very important fact is that younger voters were more likely to favor the inclusion of the two independent candidates into the debates, demonstrating a sort of changing of the guard as younger voters are not as content with the status quo two candidate system.
- Dr. Ron Paul said the majority of Americans were unhappy with the choice on offer from the mainstream parties and urged the third-party candidates to bring their supporters together to vote against the "establishment candidates". Mr Nader, Green Party candidate Cynthia McKinney, a former Democratic congresswoman for Georgia, and Constitution Party hopeful Chuck Baldwin were among those to attend the news conference.

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Original Source: CNN, Zogby International, votenader.org, and San Francisco Examiner