IOWA CITY — College students supporting Rand Paul for president were out in force going door to door in this university town recently, using their iPad Minis to help identify Republicans committed to voting for the Kentucky senator in next year’s Iowa caucuses.

And when Gov. Bobby Jindal of Louisiana visited the state the same week in June for town-hall-style meetings in Waukee, Council Bluffs and Sioux City, his supporters collected voters’ names and emails with an eye toward caucus day.

But the Paul and Jindal campaigns were not behind these time-honored grass-roots organizing efforts. Instead, in a twist that shows how even retail politics is being transformed by a flood of loosely regulated big money, the two candidates’ courtship of voters is being carried out by “super PACs,” which are using their abundant war chests to move into the nuts and bolts of campaign operations.

In previous election cycles, super PACs — which can raise unlimited donations from corporations and individuals alike — largely channeled money from wealthy donors into political advertising. But now they are branching out into what had seemed a fundamental function of a campaign committee: organizing voters one at a time.