Third Parties

In a political landscape dominated by the Democratic and Republican parties, third or minor parties have had great trouble getting rooted. Three major third parties are working to sustain a national presence and are running candidates around the country: the Libertarian Party, the Greens, and the Constitution Party. Despite their limited success in the electoral realm, third party activists argue that their ideas have influenced debate in this country.  A new group, Americans Elect 2012, is seeking to present a credible challenge to the major parties and is working to organize "the first-ever open presidential nominating process." 

According to Ballot Access News (>), for 2012 the Libertarian Party will have automatic ballot access in over half of the states, the Green Party in 14 states, and the Constitution Party in 12 states.

Libertarian Party

The 2012 Libertarian Convention will be held May 4-6, 2012 at the Red Rock Resort in Las Vegas, NV.  The Libertarian National Committee set the date and location at its meeting in New Orleans, LA on Nov. 21, 2010. Earlier a Convention Oversight Committee researched possible venues looking at "airfares to various cities, hotel costs and amenities, local affiliate strength, and endless minutiae" and split between Las Vegas and Dallas, TX.

Rules for the selection of the Libertarian Party presidential nominee are set out in the Party's Bylaws and Convention Rules (the most recent edition of which was adopted at the Party's Convention in St. Louis in May 2010). In particular see Article 11 (Conventions) and Article 14 (Presidential and Vice Presidential Campaigns) and Rule 7 (Nomination of Presidential and Vice-Presidential Candidates).
Libertarian Party || Advocates for Self Government | Cato Institute

Green Party

Rules for becoming an officially recognized candidate for the Green Party nomination for President are set out in Article X of the Rules and Procedures of The Green Party of the United States. The Party has a 17-person Presidential Campaign Support Committee co-chaired by A.J. Segneri and Tom Yager overseeing the process.  Rules for the nominating convention are here

Ballot Access News reported on Sept. 20, 2011, "On September 25, the Green Party national steering committee will begin voting on a location for the 2012 national convention. Baltimore and Sacramento have submitted bids. Both cities propose dates for the convention of July 13-15, 2012."
Green Party of the United States || Green Party Watch | The Green Institute

Constitution Party

The 2012 Constitution Party National Nominating Convention will be held April 18-21, 2012 at the Sheraton Music City Hotel in Nashville, TN.  The number of delegates per state is roughly based on the electoral vote for each state.  States that achieve certain criteria may be awarded extra votes, or in other instances a state may have a reduced vote due to past circumstances of a negative nature.
Constitution Party || Constitution Party WebRing

Americans Elect 2012

This group is seeking to organize "the first-ever open presidential nominating process" culminating in an online convention in June 2012.  Americans Elect is currently working on achieving ballot access in all 50 states.  Leaders of Americans Elect state that it is not a political party, although it is indisputably fulfilling some of the roles of a political party.  Americans Elect, which has its origins in Unity08 (see also Unity08 v. FEC), organized in April 2010 as a Section 527 organization and reorganized later in 2010 as a 501(c)(4).

Americans Elect has the potential to play a significant or even decisive role in the November 2012 general election if it does achieve ballot status in all 50 states and if voters are dissatisfied with the major party nominees and if it nominates a credible alternative ticket.  It could equally well be a non-factor.  The group's objectives appear high minded: "nominate a presidential ticket that answers directly to voters—not the political system."  [principles  |  organization  |  more]  However, there are skeptics; most notably the progressive-left Irregular Times has started up an "Americans Elect Watch" (keeping an eye on a corporate run for President").
Americans Elect 2012  |  Americans Elect Watch