Mr. Obama’s campaign says it has taken pains to discourage these efforts on its behalf, and in fact the campaign has no recourse in controlling them. “We do not think people should be donating to 527s,” said Bill Burton, a campaign spokesman. “We would rather have them involved in our campaign. It is our hope that anyone who supports Obama does so directly through his campaign and not through these outside groups.”

The Clinton campaign, which has not made an issue of outside help, has been a much greater beneficiary of these groups. Mrs. Clinton has large unions representing government employees and teachers on her side, as well as the politically savvy feminist organization Emily’s List. The two unions plan to spend millions of dollars on her behalf through direct mail, phone banks and get-out-the-vote efforts in Super Tuesday states.

The teachers’ union, which has 1.4 million members, has budgeted $3 million for the effort, while the government employees’ union has earmarked $5 million. Meanwhile, Emily’s List has an effort directed at women just outside the New York City media market.

Mr. Obama has lined up support from unions representing plumbers and pipefitters, as well as hospitality and garment workers. One union, Unite Here, plans to mobilize its 450,000 members through direct mail advertisements, phone banks and door-to-door visits in Super Tuesday states. It will also continue efforts, begun in Nevada, to run pro-Obama television and radio spots, many in Spanish and aimed at voters in California. The plumbers’ and pipefitters’ union, which has 340,000 members, said it was working with the Obama campaign to get out its membership and was encouraging members to donate time as Obama campaign volunteers.

Unlike 527s, unions can coordinate some activities with campaigns, and spending by their political action committees must be reported to federal regulators.