Arthur M. Schlesinger Jr., writing on April 27, 1967, described the mutability of attitudes toward presidential power. The excerpt is from “Journals: 1952-2000,” a collection of the late historian’s diary to be published next month.

We are reaching some sort of crisis on Vietnam. L. B. J. has evidently decided on a quick and brutal escalation of the war. It was clear in February that he did not wish negotiation until the existing military balance could be turned considerably in our favor; and his clear intention now is to bomb North Vietnam until Hanoi is prepared to sue for peace on terms which will meet Rusk’s idea of a satisfactory settlement.

More than that, the administration is apparently determined to advance the proposition that dissent is unpatriotic, and has brought General Westmoreland back for this purpose.

The irony is that all of us for years have been defending the presidential prerogative and regarding the Congress as a drag on policy. It is evident now that this delight in a strong presidency was based on the fact that, up to now, all strong presidents in American history have pursued policies of which one has approved. We are now confronted by the anomaly of a strong president using these arguments to pursue a course which, so far as I can see, can lead only to disaster.

It is not hard to assert a Congressional role; but, given the structure of the American system, it is very hard to see how the Congress can restrain the presidential drive toward the enlargement of the war. Voting against military appropriations is both humanly and politically self-defeating. The only hope is to organize a broad political movement; and even this cannot take effect until, at the very earliest, the 1968 primaries, which may be too late.