McGovern Woos O'Brien, Meany

George McGovern acted yesterday to widen his support among Democratic regulars by confirming his choice of Lawrence O'Brien to remain as head of the Democratic National Committee. And he announced he will seek a fence-mending session this week with AFL-CIO president George Meany.

But the South Dakota senator and leading contender for the Democratic presidential nomination would not close the door on the possibility he will refuse to support the nominee if he is someone other than himself.

He said again he expects to win back the 151 California delegates he lost in a Credentials Committee action last week and go on to win the nominations.

McGovern has termed the committee's action "an incredible, cynical, rotten political steal." He said at the time he "couldn't possibly support a convention that would sustain this kind of shabby, back-room dealing. I wouldn't have any part of any convention nominee who would support this."

Meanwhile, President Nixon worked yesterday on the strategy and tactics of his re-election effort and telephoned his just-resigned campaign manager, John Mitchell, to "express his understanding" of Mitchell's decision to quit full-time politics.

Press secretary Ronald L. Ziegler reported Nixon's early-morning call to Mitchell, former attorney general and long-time Nixon friend. Mitchell resigned as campaign director Saturday after receiving an ultimatum from his wife, Martha, to get out of politics or she would leave him.