The formation of a super PAC in support of Newt Gingrich adds a new committee to an already crowded field. Eight of the candidates running for president in 2012, including President Obama, have at least one super PAC that has been formed in their behalf. As of now, former Pennsylvania Sen. Rick Santorum is the only candidate without one.

Super PACs, or “independent-expenditure only committees,” as they are officially known, are a relatively new kind of political action committee (PAC) that can raise unlimited amounts of money for a candidate or cause from corporations, unions, individuals, etc. The rise of the super PAC started in the most recent midterm cycle, after the Supreme Court’s ruling in the Citizens United case lifted federal and state campaign spending regulations dating back to the 1970s.

Super PACs have since become ubiquitous. Seven of the eight leading GOP candidates have at least one that is raising money in their behalf; a couple of the candidates have more than one. Earlier this month, a group calling itself “Texas Aggies for Rick Perry” filed papers with the Federal Election Commission. The name refers to Perry’s alma mater, Texas A&M University, and the group is the second super PAC operating in Perry’s behalf, in addition to his “Make Us Great Again” PAC, which formed in July.

The candidates are prohibited from having any connection to the super PACs, meaning they can also distance themselves from any negative campaign ads against their opponents that are funded by the super PACs. The groups can also pay for polling, mailing materials, social media efforts and research, among other things.

Rep. Michele Bachmann’s presidential campaign also has two super PACs formed in its behalf: “Keep Conservatives United,” which was formed in July, and “Citizens for a Working America”, which was originally formed in the 2010 midterm elections with the purpose of defeating Democratic incumbent Rep. John Spratt of South Carolina. The group was repurposed in August to support the Minnesota congresswoman’s campaign.

The committees are independent expenditures and the campaigns they are backing keep their distance. They have to. Super PACs are forbidden from directly coordinating with the campaigns they are formed to support, which can make it difficult to keep track of the various groups as they crop up, and as they go away.

Many Super PACs form with a specific mission, and they will shut down after they believe it has been achieved. For example, a pro-Perry super PAC called “Veterans for Rick Perry” folded in early September, shortly after he officially launched his presidential campaign. The group’s founder, Dan Shelley, released a statement Sept. 9 explaining that “Veterans for Rick Perry” had accomplished its mission and would therefore be leaving the next step to the official Perry campaign.

“Veterans for Rick Perry was created to demonstrate veterans’ support for a Rick Perry presidential run, and to draft him into the presidential race. Mission accomplished!” Shelly wrote. “With our objective of encouraging Governor Perry to enter the presidential race accomplished, we have filed the necessary papers to dissolve the non-connected committee, shut down this outfit and entrust next stage logistics to the official Rick Perry presidential campaign.”

Super PAC’s have already played a significant role in fundraising in the 2012 cycle, and as the campaign season drags on, others are likely to come and go.