Sounding at times like the New Deal Democrat he was 40 years ago, Ronald Reagan today promised blue-collar workers he would rejuvenate the economy if he is elected president.

"I happen to think that the best social program is a job," Reagan told an approving crowd of hard-hatted workers at a subway tunnel construction site.

Reagan won loud applause when he said he would remove federal bureaucratic roadblocks to the Westway Project, a $1 billion-plus highway and park plan that would replace New York's decrepit West Side Highway. And he received even louder applause when he pledged to name an Environmental Protection Agency administrator who would use "common sense" in his approach to construction projects.

Some environmentalists object to Westway, begun under President Ford and delayed during the Carter administration, on grounds it would increase traffice congestion and air pollution in New York City. But the project is ardently supported by the construction industry and its trade unions. Reagan's central strategy in this election campaign is to peel away normally Democratic blue-collar votes in key industrial states. Every speech and statement he made today was directed to this purpose.

In Paterson, N.J., Reagan pledged his support to tuition tax credits for parochial schools, "as soon as it is fiscally possible," and observed that President Carter opposes such credits.

"Separation of church and state doesn't mean we have to separate ourselves from our religion," Reagan said.

In heavily Catholic Wilkes-Barre, Pa., there was more praise for tuition tax credits plus a familiar promise to revitalize neighborhoods by giving tax incentives to small buinesses and a pledge to make certain "that the Social Security system is sound and protected."

In this rich, coal-producing region, Reagan called attention to the fact that 22,000 coal miners, are out of work, and said he would work to encourage the growth of the anthracite coal industry as well as to develop new energy sources.

Everywhere he went, starting with a breakfast speech in New York City to small businessmen, Reagan's basic theme was jobs and more jobs.

This blue-collar emphasis was in sharp contrast to the tuxedoed splendor of the evening before, when Reagan, accompanied by Ford, addressed a black-tie fund-raiser at the Waldorf Astoria that was shown on closed-circuit television in 21 other cities. The combined fund-raisers grossed $6 million, including $1.6 million at the Waldorf affair, where Reagan was introduced by Frank Sinatra to the strains of "New York, New York."

Buoyed by the fund-raiser, Reagan was in good spirits today when he arrived at the subway tunnel construction site and was presented with a hard hat that did not fit.

"You know I've got a pinhead," said Reagan. "I'm afraid this will be too big."

In his appeal for Democratic votes, Reagan quoted freely from a pantheon of Democratic political heroes -- Franklin Roosevelt, John and Edward Kennedy, Harry Truman, Al Smith.

And when a New York reporter asked Reagan whether he "really expected a conservative Republican to make a dent in this town," Reagan replied: "Well, maybe a conservative Republican who also goes back to Roosevelt's New Deal. I was a New Deal Democrat. I found in recent years that the leadership of the Democratic Party doesn't have anything in common with the Democratic Party I grew up in, and that's why I switched."

Reagan arrived in Pennsylvania today with a Gallup Poll, commissioned by the Pittsburgh Post-Gazette, showing him leading Carter 40 to 33 percent in the state, with John B. Anderson at 16 percent.

As part of his appeal to normally Democratic voters, Reagan said in Pennsylvania that he agreed with President Carter that the United States should oppose any attempt by the U.N. General Assembly to expel Israel.

Reagan said that the United States should exercise a veto of any such move in the Security Council because the U.N. charter provides that nations can be expelled only upon recommendation of the Security Council. He said that if the United States proved unsuccessful in its effort, the U.S. government should suspend all financial contributions to the world organization "and urge our friends to do the same until the rights of Israel are fully respected."