Ullman first ran for Congress in in 1954. In a year that was generally good for Democrats – especially in Oregon – he lost to Republican Sam Coon, following the resurrection of a two-year-old charge of a violation of the Real Estate Code. Even the Republican-leaning Oregonian considered the allegations to be politically motivated. Ullman ran successfully for the seat in 1956, defeating Coon. Ullman won by waging a populist campaign focused on issues regarding public power, of which Ullman was a fierce proponent, and whether the hydroelectric development of Hells Canyon on the Snake River should be turned over to private interests, which Ullman opposed. Ullman represented one of the largest districts in the nation that did not cover an entire state. His district stretched from the state capital of Salem all the way to the Idaho border. It encompassed roughly, an area larger than any state east of the Mississippi River—and included alpine forest, rangeland, and desert. While in Washington, he devoted himself to the development of Oregon's water resources and the improved management of public lands and national forests. Committees Ullman served on:
For most of his Congressional career, Ullman was viewed as a moderate Democrat. Among other things, Ullman is regarded by many as the father of the present-day United States budget process. In 1973, he initiated and later co-chaired the Joint Study Committee on Budget Control, leading to major budget reforms which, for the first time, required Congress to reconcile spending with revenues in order to address mounting federal deficits. He also served as chairman of the new House Budget Committee in 1974. In 1975, Ullman ascended to the chairmanship of the House's powerful Ways and Means Committee, on which he had served since 1961. As chairman, he oversaw the drafting and enactment of numerous major tax reform bills. For example, as The New York Times noted, "Among Mr. Ullman's most important actions as committee chairman was his sponsorship of sweeping legislation to cut taxes in an effort to help shore up the United States economy. His bill, which gave more than $20 billion in income tax rebates to Americans in the spring of 1975, brought the Oregon Democrat national recognition after almost two decades of relatively quiet Congressional service." Ullman also played a central role with respect to other key legislation, including the Windfall Profits Tax Act of 1980, which redirected an estimated $79 billion of oil companies' profits resulting from price deregulation toward support for mass transit, oil price relief for poor families, and the development of alternative energy sources. On many regional issues, Ullman was a de facto leader of the Pacific Northwest's Congressional delegation, along with Senator Henry "Scoop" Jackson and congressman Tom Foley. In addition, Ullman was well known for his longstanding advocacy on behalf of American Indian tribes in Eastern Oregon, which he felt had historically been treated unjustly by the federal government with respect to treaty, land and other issues. In the midst of the "Reagan landslide"—which also led to the defeat of President Jimmy Carter and the Republican takeover of the United States Senate—Ullman narrowly lost his bid for a thirteenth term from the Second District to Republican challenger Denny Smith. Ullman's electoral defeat was widely attributed to the nationally prevalent anti-incumbent and anti-government mindset; the presence in his House race of an independent candidate; the increasing conservatism of the Second District; to his advocacy for a value-added tax similar to that now used in the European Union and other nations as a partial alternative to what he viewed as inequities in the existing Federal income tax system; and to the decision of President Jimmy Carter to concede defeat in the 1980 presidential election before the polls in Oregon were closed, an act which Ullman and others believed discouraged many people from voting.
After politics
After leaving office in 1981, Ullman remained in Washington D.C. and established Ullman Consultants, Inc., a consulting firm in Georgetown, with his wife Audrey and former members of his Capitol Hill staff. In 1981, Ullman gave his extensive Congressional papers to the University of Oregon. He lived in Arlington, Virginia and Falls Church, Virginia until his death due to prostate cancer on October 11, 1986.