Dirty Fucking Hippie(s). A person who's political views were once considered the mainstream of the American Democratic Party (i.e. Franklin Delano Roosevelt, Harry Truman, the Kennedys). Largely the base of the Democratic Party, they make up the bulk of activists who donate, volunteer and organize for Democratic candidates every election. DFH tend to want greater government transparency, return to fundamental ethical principals, reform of the markets and health care system among other things. While generally treated as extremists by political opponents and the media, DFH views generally are in the mainstream of American opinion as evidenced by political polling research.
After the ascendancy of Ronald Reagan, the Democrat Establishment moved to the right and began to marginalize it's own base in an effort to capture more Republican votes. Reform minded Democrats are sneered at by the Democrats in DC as "out of touch flakes" who "don't know how things work in Washington". Their opposites in the Democratic Party consider themselves "centrists" but tend only towards undermining New Deal Reforms, have pro-corporatist agendas and tend to flinch when criticized by Republicans. They cannot pass any legislation until it is approved by someone in the Republican caucus.
Howard Dean is considered a DFH.