Sen. Maria Cantwell is the low-income housing tax credit’s (LIHTC’s) biggest champion in Congress.

A longtime supporter of the federal program, the Democrat from Washington state has stepped forward in recent years to become the go-to legislator on issues involving the housing credit, the nation’s main program for developing and preserving affordable housing.

At a time when the number of renters paying more than 30% of their income for housing reached a record 21.3 million in 2014, affordable housing needs key supporters in Congress.

“Sen. Cantwell is among the most respected lawmakers in Washington [D.C.] for the hard work she puts in on many issues, including affordable housing,” says Bob Moss, principal and national director of governmental affairs at CohnReznick. “Whether the issue is education or housing, she is a fierce advocate and tireless leader who grew up in a strong working-class family. She has never forgotten those values.”

Cantwell’s experience includes briefly serving in the House of Representatives and working as a successful businesswoman in Washington [state’s] high-tech industry before being elected to the Senate in 2000.

This year, the senator introduced legislation to expand the LIHTC by 50% to help create or preserve about 1.3 million affordable homes over a 10-year period—an increase of 400,000 more units than is possible under the current program.

Sen. Orrin Hatch (R-Utah) is co-sponsor of the bipartisan bill, S. 3237. He’s chair of the powerful Senate Finance Committee, of which Cantwell is a member.

“Affordable housing is a crisis all across America,” Cantwell said when introducing legislation to expand the LIHTC. “With skyrocketing rents and an increase in homelessness, more affordable housing units are a necessity.”

What’s impressive is the effort Cantwell is putting behind the legislation. She’s held several events at affordable housing developments in New York, Seattle, and other cities to raise awareness about the lack of affordable housing and the importance of the housing credit.

As part of her campaign, she also issued a report detailing how the LIHTC was responsible for financing the development of nearly 2.9 million rental homes that housed more than 13.3 million people between 1986 and 2013.

“It is uncommon to have a champion on Capitol Hill who needs no prodding or encouragement to engage in an issue, but Sen. Maria Cantwell is anything but common,” says David Gasson, executive director of the Housing Advisory Group and vice president of Boston Capital. “From the moment our industry raised the issue of meek resources in the face of unfathomable demand for affordable housing, she and her staff dove into the issue and rallied her colleagues to support our programs.”

Cantwell was among the key supporters who successfully established a minimum 9% LIHTC rate last year. The move was a critical improvement for the program, giving developers the certainty of a fixed rate.

“Her determination resulted in the passage of the 9% fixed LIHTC and has put us in a strong position to secure additional resources in the face of tax reform,” Gasson says.