Rep. Tim Ryan snags one of Bernie Sanders' top Iowa aides

But D'Alessandro, who recently came up short in a Democratic congressional primary, tells CNN he's not telegraphing a message about his 2020 allegiances. His agreement with Ryan is good only through the end of this year, and it isn't exclusive.

"Obviously, if Bernie Sanders comes in and says, 'Pete, I'm doing an event and I'd like you to help me,' I'd go and help him," said D'Alessandro. "I think Tim understands that."

He added, "My folks that I talk to in Bernie world are very aware of it, and nobody said not to do it."

D'Alessandro agreed to help Ryan after the Ohio Democrat lent his support to D'Alessandro's congressional bid.

"Tim Ryan was out here helping me. He was just such a great supporter in every way, who was there as a friend when I would ask him for advice," said D'Alessandro. "He certainly didn't need to weigh in on the guy who was going to finish third, and the fact that he did that for me ... whatever he decides to do, (helping him) just seemed like absolutely the right thing to do. Maybe that transcends politics."

D'Alessandro also praised Ryan for his "compelling" story, as a Rust Belt Democrat "who was willing to take on establishment" by challenging House Minority Leader Nancy Pelosi. D'Alessandro touted Ryan's "authenticity," saying: "One thing that came clear to me in 2016 working for Bernie -- what you're talking about matters, that's the first place you bring people in -- but people are just crying for authenticity and this guy is as authentic as the day is long. And I think that's going to be one of the things people realize right away."

In his work for Ryan, D'Alessandro will connect him with state lawmakers and party activists for meetings and events, although he said he believes Ryan is already "doing the right things" in Iowa to test the waters. Ryan is slated to headline the Iowa Democratic Wing Ding event next month along with Rep. John Delaney, a Maryland Democrat who has already announced his bid for president.