Ever since the Supreme Court permitted political committees to raise unlimited sums for independent spending, the super PAC has occupied a growing place in the political ecosystem. The 2012 version of presidential super PACs mainly paid for ads. Restore Our Future, the PAC supporting Mr. Romney, spent 97.6 percent of its $142 million in independent expenditures — messages advocating Mr. Romney’s election or the defeat of his opponents — on broadcast ads and mail. Priorities USA Action, which backed Mr. Obama, spent almost exclusively on TV, radio and online advertising, according to Federal Election Commission records. Together with the national parties, both sides managed to raise and spend nearly $2 billion. Some donors balked at giving large amounts of money for negative television ads, so a Democratic super PAC was created to help conduct opposition research.

A handful of super PACs tried get-out-the-vote operations in 2012, mostly robocalls, but none of the ones tied to presidential candidates did so. But during the 2014 midterm elections, super PACs tried their hands at other campaign activities, including voter turnout efforts, particular in high-profile Senate races. The Alaska SalmonPAC, for example, spent more than $788,000 on field canvassing in support of Mark Begich, the Democratic senator who lost his seat to Dan Sullivan, a Republican. Environmental and abortion rights groups also spent heavily on field operations in states such as North Carolina and Colorado.

We’ve seen an expansion of this in the early part of the 2016 campaign. NextGen Climate Action, the nonprofit founded by Tom Steyer, a billionaire investor, is an example. Its components include a 501(c)(4) organization, which can spend money on electoral politics as long as it isn’t the primary activity, and NextGen Climate Action Committee, a super PAC that aired advertising and paid for get-out-the-vote efforts in 2014. Mostly funded by Mr. Steyer, the organization is able to maintain its activities even in years with no major federal elections. In February, with an eye to the 2016 Iowa presidential caucuses, the NextGen super PAC bought the campaign list of Bruce Braley, the Iowa Democrat who lost a Senate race last year.

Why? A super PAC mainly focused on television advertising would have little need of such a detailed list of Iowa Democratic voters and their preferences. But because NextGen has also paid for door-to-door canvassing programs, spending $177,000 for the Iowa list gives it an important tool. Last fall, the Planned Parenthood super PAC paid Community Outreach Group LLC hundreds of thousands of dollars for voter canvassing work in Senate races in Alaska and North Carolina, F.E.C. records show. Community Outreach Group is a part of Planned Parenthood that acts as a vendor to Planned Parenthood groups. The conservative nonprofit Americans for Prosperity also spent millions on an extensive field operation in the 2014 elections.