During the 1960s, these unions were strong supporters of the Democrats and delivered strong voter turnout for John F. Kennedy, Lyndon Johnson and Hubert Humphrey. Affirmative action John Lindsay was elected Mayor of New York City in 1965 as a liberal Republican pledging to take on special interests, including the building and construction unions. In the late 1960s, a diverse coalition of business leaders, construction companies, civil rights activists, reformers and the media wanted to open up opportunities for minorities. A study by the New York City Commission on Human Rights in 1967 found that minority membership in the six most highly skilled building trades was only 2 percent and had not changed since 1960. The reform coalition thought the low entry into the building trades increased building costs above the market rate and cost New York City millions of dollars in increased costs. In 1968, the Lindsay administration issued Executive Order 1971, which required city contractors to sign a non-discriminatory hiring action plan and develop affirmative action plans. If the contractors did not comply with the executive order, they could not bid for city work. Brennan was strongly opposed and promised to take action to have the order rescinded. The Nixon Administration, under Labor Secretary George P. Shultz, announced the Philadelphia Plan in the summer of 1969 to increase minority membership of skilled building trades to twenty per cent within five years. Brennan and the skilled labor unions were determined to stop the introduction of such a system. They persuaded George Meany, President of the AFL-CIO and a former plumbing union official in New York City, to sponsor Congressional and legal challenges to the plans, but these efforts failed. In February 1970, the Labor Department announced that it would support local construction industry affirmative action hiring plans provided that they were consistent with the Philadelphia Plan. Brennan was having a great deal of trouble persuading either the Department of Labor or the Lindsay administration to his way of thinking. The Lindsay administration stated that it wanted 4,000 minority trainees as part of the plan, but Brennan wanted no more than 1,000 trainees. Schultz warned labor leaders that the federal government would implement the Philadelphia Plan in 18 cities if suitable local plans were not implemented quickly. Hard Hat Riot On May 4, 1970, four students were shot dead at Kent State University in Ohio while protesting the Vietnam War