Wis. — On the final weekend before Tuesday’s closely watched Wisconsin primary, hundreds of Republican voters streamed into a hotel ballroom here to see Sen. Ted Cruz, who brought along Gov. Scott Walker and former Green Bay Packers defensive lineman Kabeer Gbaja-
Biamila to make a final pitch.

The only inkling that this was not a typical campaign event were the staffers wearing green “KTP” badges stationed at the doors. They worked for Keep the Promise, a super PAC allied with the Republican presidential candidate. Instead of handing out Cruz campaign material, they were distributing “Choose Cruz” signs and stickers paid for by the group.

In recent months, the super PAC has been effectively serving as an extension of Cruz’s official campaign, hosting major rallies for him from South Carolina to Utah. The senator from Texas appears at the events as a “special guest,” an arrangement that takes advantage of the loose federal rules governing how campaigns and super PACs can interact.

Since January, Cruz has appeared at nearly 20 rallies that Keep the Promise PAC has organized, often alongside well-known surrogates such as conservative talk show host Glenn Beck and Phil Robertson of “Duck Dynasty.”

The tactic serves to offload costs onto the super PAC, which has been financed by six-figure checks from wealthy Cruz supporters — allowing Cruz to harbor his resources for a drawn-out Republican nomination battle with front-runner Donald Trump.

Although his campaign raised more than $66 million by the end of February, Cruz entered March with just $8 million left in the bank. Keep the Promise had less than $1 million in cash at the end of February, but the super PAC can quickly replenish its coffers because it can accept unlimited donations from individuals and corporations.

Cruz spokeswoman Alice Stewart said the campaign was not short on cash. “I can assure you we are doing quite well with fundraising, so that is not an issue,” she said.

Stewart said that the senator is invited to speak “at a wide variety of events,” adding that the campaign’s attorneys make sure his appearances comply with campaign finance rules.

The role that Keep the Promise is playing in hosting campaign-style rallies for Cruz — who is backed by at least eight different super PACs — provides new fodder for Trump, who touts his independence as a billionaire using his own money to fund much of his campaign. He has also disavowed super PACs, although one group recently began spending money on his behalf.

“This is financial corruption of the highest order, and further proof that Lyin’ Ted Cruz is totally owned by donors and special interests,” Trump spokeswoman Hope Hicks wrote in a statement, using Trump’s regular insult for Cruz. “Our entire political system has been corrupted by special interests who want to drive down wages and incomes, and Ted Cruz has now been unmasked as their favorite pawn.”

In response, Stewart noted that Trump has received millions in contributions.

“What’s surprising here is Donald’s continued lack of honesty with the voters about how he’s paying for his campaign and who he hopes will pay for his campaign in the future,” she said. “Not only has Donald raised more than $9.5 million, despite claims of self-funding — his campaign manager is a lobbyist, the operative brought in to run his delegate operation is a ­lobbyist, and Donald recently ­hobnobbed with a dozen high-
powered special interest lobbyists in Washington to see where they shared mutual interests. Make no mistake about it, Donald Trump is the Washington Cartel.”

Keep the Promise’s move into event production shows how super PACs allied with this year’s presidential candidates have expanded their portfolios beyond expensive television campaigns. The big-money groups — which are not allowed to coordinate their paid advertising strategy with candidates or political parties — have taken on policy research, rapid response and field organizing as they seek new ways to bolster their favored candidates.

Last fall, super PACs supporting Louisiana Gov. Bobby Jindal and former Hewlett-Packard chief executive Carly Fiorina, both Republicans, sponsored campaign-styletown halls.and rallies featuring their candidates, handling the promotion, logistics and staffing

In doing so, they were relying on advisory opinions issued by the Federal Election Commission giving candidates permission to appear as guests at super PAC fundraisers, as long as they do not ask supporters to donate more than $5,000.

“There is specific FEC guidance that it is permissible for candidates and their surrogates to appear at events, as long as they are not soliciting soft dollars,” said Stefan Passantino, an attorney for Keep the Promise PAC. “It’s perfectly legal.”

But advocates for stricter campaign finance regulations said the arrangement shows how super PACs financed by wealthy contributors are increasingly operating in conjunction with campaigns, violating the principle of independence that the Supreme Court laid out in its 2010 Citizens United v. FEC decision.

“It just tilts the system even more to the super-rich,” said Nick Penniman, executive director of ­Issue One, a bipartisan group working to reduce the influence of wealthy interests on politics.

Larry Noble, general counsel of the nonpartisan Campaign Legal Center, said that if a super PAC is coordinating with a campaign to schedule a rally, the money it spends to produce the event could be considered an in-kind donation.

“It’s one thing to have a candidate appear at something billed as a super PAC fundraiser,” he said. “What this has morphed into is the super PAC putting on campaign events, and that is illegal.”

Passantino rejected that argument. “The campaign simply responds to our requests as to the availability of any invited guests,” he said. “All other details are handled by PAC staff in conformity with FEC regulations and guidance.”

Keep the Promise officials decided to start regularly producing rallies featuring Cruz after the group hosted such events in Iowa and saw how popular they were, according to super PAC spokeswoman Laura Barnett. She said the super PAC makes all the arrangements, choosing dates close to a primary when Cruz probably will be in the area.

For supporters in the audience, however, the fact that a super PAC is sponsoring the rally is often a lost distinction.

“I didn’t know anything about the super PAC or his campaign and I’m not sure how that works,” Cindy Kennard, a 54-year-old librarian who went to see Cruz at a Keep the Promise event in Provo, Utah, last month. “I just heard he was coming to Utah for a rally.”

Steve Matz, a Cruz supporter from Franklin, Wis., who attended a Monday evening rally in Waukesha hosted by Keep The Promise, said he did not realize the group was a super PAC. But that made no difference, he said.

“Cruz is in my backyard and I came to see him,” he said with a shrug.

Katie Zezima in Washington and Provo, Utah, and Sean Sullivan in Green Bay and Waukesha contributed to this report.