Ronald Reagan tonight brushed aside george Bush's victory in the Republican popularity contest in Pennsylvania. Reagan said his victory in the Pennsylvania delegate contest had brought him to the brink of the Republican presidential nomination.

"Our estimate -- our conservative estimate -- shows that today we already have won, or can reasonably count on at this early date nine-tenths of the delegates needed to win the nomination," Reagan said in a statement issued within minutes of network projections of Bush as the winner in Pennsylvania.

The Reagan statement said the week just ended was "the very best of this campaign" and looked forward to victories in the May 3 primary in Texas and the May 6 primaries in Indiana, North Carolina and Tennessee, which Reagan won four years ago.

Bush's win in the popularity contest came as a mild surprise to the Reagan camp but did not change the thrust of what key Reagan aides have been saying the past two days. Earlier today Reagan strategist and pollster Richard Wirthlin told reporters that Reagan could count on about 900 of the 998 delegates needed for the GOP nomination.

Most of those delegates are already chosen, but the figure includes 168 delegates from the winner-take-all primary June 3, in California, where a recent poll showed Reagan leading Bush by 7 to 1.

Earlier today in South Bend Reagan said he would "look closely" at the desirability of applying anti-trust laws to labor unions.

Responding to a question at St. Mary's College here, Reagan said some labor union leaders have become too powerful.

". . . We should look very closely at whether they should be bound as businesses are by the antitrust laws." Reagan said.

Afterward, at a press conference, Reagan was vague about what remedies he would seek against unions and said he would ask "legal advice" on the issue. h

His criticism seemed to be less of any economic abuse of power than of alleged political abuses. He gave the example, which he said came from a Reader's Digest article written by Al Barkan, head of the AFL-CIO's political arm, of how $68 million had been poured into a presidential campaign of the late Sen. Hubert H. Humphrey.

Antitrust laws were intended as a legal weapon against corporations seeking to combine their economic might to control a market. In the late 1950s, some conservative groups sought to bring unions under antitrust control in an effort to limit national industrial bargaining.

Reagan observed that he was a six-time president of the Screen Actors Guild. He said the guild had defied the AFL-CIO and refused to allow contributions from its members to be used for political purposes.

Some aides regretted Reagan made his statement while he is trying to appeal to union members to join what he called a "new coalition." But one aide shrugged and said, "Reagan's goingo to say what he thinks. That's the way it is and there's nothing any of us can do about it."

Edwin Meese, Reagan's chief of staff, said the candidate took a similar position in 1976.

Reagan was greeted emotionally at St. Mary's, a Catholic women's college adjacent to the University of Notre Dame, and he recalled coming to the campus many years ago to play the role of Notre Dame football hero George Gipp in what was Reagan's first starring role.

"For ourselves, our families and our country, we will win for the Gipper in 1980 by electing your president," said Notre Dame junior Greg Folley, as he presented Reagan with a Notre Dame football jersey. "May the luck of the Irish be with you."

The blue-and-gold jersey was inscribed "gipper" and bore the big numerals "80."

In campaigning today in Evansville, South Bend and Layfayette, Reagan concentrated on areas that Indiana strategist Keith Bulen said would be targets in a race against President Carter.