Democratic state Sen. Linda Valentino, a longtime legislator from Saco, is expected to announce Sunday that she will not run for re-election, according to several Democratic sources.

Reps. Barry Hobbins and Justin Chenette, both Democrats from Saco, announced Saturday they each plan to run for her seat. The Saco legislators said that Valentino plans to announce her decision to retire from politics following the caucus on Sunday.

“Barring a last-minute reconsideration by Sen. Valentino, my hat’s in the ring,” Hobbins said in a press release.

Chenette, who is serving his second term in the House, said he has long considered Valentino a close mentor and friend.

“I want to continue the legacy she’s laid down, which is focused on working hard for our constituents, fighting for our community and bringing people together,” he said.

Nomination papers are due March 15. Hobbins and Chenette would face off in a June primary.

Valentino did not return phone calls Friday and Saturday.

Valentino, who served four terms in the Maine House, is in her second term in the Senate and would have been eligible under Maine’s term-limit law to serve two more terms. She was elected to the seat representing Saco, Old Orchard Beach, Hollis, Limington and part of Buxton when Hobbins termed out.

Hobbins said Valentino has “served her district with distinction.”

“Linda has explained her reasoning to me, and she is completely justified, but not having her in the Senate will be a tough loss for the area,” Hobbins said. “She was elected to the Senate as a very seasoned legislator, having first served eight years in the House of Representatives. She already knew the legislative process thoroughly when she arrived as a senator, and that veteran experience really helped our community in Augusta.”

Hobbins, House chairman of the Legislature’s Judiciary Committee, has served five terms in the Senate and is in his eighth term in the House.

He was first elected when he was 21, the youngest Maine legislator in history at the time, he said. He served in the Senate from 1988 to 1990 and 2004 to 2012. He was the Senate Democratic floor leader from 2010 to 2012.

Hobbins said he grew up with Valentino in Saco and understands why she feels the need to step down from public service.

“Down here, family comes first,” he said.

Although he wishes it were under different circumstances, he welcomes the opportunity to serve again in the Senate, where, he said, “I think I can be more effective.”

Chenette, 24, was the youngest House member and the youngest openly gay legislator in the country when he was first elected at 21. He grew up in Saco, where he got his start in politics as a student appointed to the state Board of Education. He now runs a small multimedia company, Chenette Media LLC, and the nonprofit Saco Bay Center for Civic Engagement.

Chenette said he decided to run for Valentino’s seat to bring a new perspective to the office.

“As a small-business owner, I do see the challenge of operating a small business in Maine,” he said. “We need new blood and new energy in Augusta to hit the reset button.”