Rick Santorum sent a teasing tweet earlier today with few details: "@RickSantorum: I have a big announcement coming on Friday! Stay tuned!"

Longtime Santorum adviser John Brabender tells ABC News Santorum will announce what he's doing next after his failed presidential bid, but he wouldn't reveal much more. The former presidential candidate has written in fundraising emails to supporters that he will let them know what's next for him as soon as he is able to retire his campaign debt. After the last reporting period, the  Santorum campaign owed $2.2 million.

Brabender said Santorum will not announce that he's running for another elective office.

Two other insiders familiar with Santorum's thinking said the announcement could have more to do with the issues that Santorum plans to pursue through his political action committee.

Last month Santorum's superPAC, the Red, White, and Blue Fund,  became a hybrid political action committee that will also work as a traditional leadership PAC to push Santorum's message, support his political travel, cover administration costs and donate money to candidates he supports with similar views. No matter what the announcement, it's likely this newly formed organization will be running the operation.

Could Santorum  announce he's campaigning with his former rival, Mitt Romney? During their May meeting the two did discuss it and Brabender said at the time "exciting the base" was an issue that came up.

"They both have different states they won, different targets," Brabender said on May 4th, referring to the different parts of the party from which the two got support. "I think it was more how can we combine what we both learned to make sure we win in the fall. Clearly Rick Santorum is a champion in the social conservative realm, with blue collar Republicans, and he wants to keep that energy going in the fall."

On Monday, Brabender said it was too early to tell where and if they would be campaigning together, saying there is "nothing scheduled" and the Romney campaign has put in "no official request" for Santorum to rally supporters on Romney's behalf. Brabender did say the campaign asked Santorum to make videos for state conventions calling on supporters to "unite behind Romney," which he did.

Friday will be a busy day for the former Pennsylvania senator. He is also headlining a fundraiser in Dallas for the Tea Party candidate in the Texas Senate race, Ted Cruz.

Two weeks ago Santorum backed Cruz, who is now in a runoff race with Lt. Gov. David Dewhurst.  Dewhurst, who is backed by Texas Gov. Rick Perry, did not get 50 percent of the vote on May 29, ensuring a Cruz-Dewhurst face-off on July 31.

ABC News' Michael Falcone contributed to this report.