It has become fashionable among a certain group of pundits and political scientists to blame the reforms undertaken by the Democratic Party after its 1968 convention for all manner of political ills - declining voter participation, the proliferation of single-issue groups, weak presidential leadership, poor congressional performance and, above all, the decay of the political party.

So great has been the hostility to these reforms, to the reformers who perpetrated them and to the proliferation of presidential nominating primaries that followed in their wake, that one expects any day now to see a book published that blames these reforms, not only for our political ills, but for cancer, heart disease, and falling arches.

Mercifully, James W. Ceaser's Presidential Selection is neither that book nor solely devoted to a diatribe against the Democratic Party's reforms.

It is, in fact, two books: a thoughtful, scholarly, readable and highly useful history of the evolution of the presidential nomination and election process; and an inaccurate, poorly researched and reasoned account of the author's distaste for the post-1968 party reforms.

Like the little girl with the curl, his good book is very good indeed; his bad book is horrid.

Ceaser's good book moves through American history in quantum leaps, touching down at those critical junctures where he perceives major changes to have taken place both in the methods of selecting presidents and in elite opinion as to the nature of the presidency. He identifies five such junctures:

The Founding Fathers' concept of a president elected on a nonpartisan basis who would be a man of sufficient character, possessing a sufficient national mandate to transcend sectional and class difference, political inaction and stalemate.

Jefferson's first tentative foray into partisan politics and his belief that at some historical junctures differing interpretations of the Constitution would create partisan division even among the theoretically nonpartisan leaders he believed desirable.

Martin Van Buren's wholehearted endorsement of two-party competition and of political leaders who were brokers between competing interests and were products of and responsible to their party.

Woodrow Wilson's rejection of both the corruption and the stalemate of party government, his call for strong and visionary national leadership and his reliance on the popular vote both in intraparty primaries and in general elections to produce such leaders.

The modern mixed system of partisan primaries and party caucuses which Ceaser believes will produce leaders with a sufficient popular mandate, but whose ambition and potential for political dmagoguery would be restrained by responsibility to party.

Ceaser's bias - stated and argued - is for institutional constraints on presidential power rather than for charismatic leadership. He fears abuse of power more than inaction, demagoguery more than indicisiveness.

As such, his good book serves as a useful corrective at a time whe dissatisfaction with the presidency of Jimmy Carter has made many forget the excesses of those who led the nation only 5 and 11 years ago.

Ceaser's bad book, on the other hand, at best reveals the limitations of viewing social change solely through the perspective of the intellectual historian and at worst plays fast and loose with the truth.

American political parties were not, a Ceaser claims, substantially weakened by post-1968 procedural reforms. American parties were already weak owing to a number of factors, including: public perceptions of local corruption and the rise of civil service; the coming of the New Deal and the transfer of hiring power from the local party to the federal government, and perhaps most importantly, the advent of television as America's primary mode of mass communication and of television advertising as the primary means of national and state-wide campaigning.

The reformers were not, as Ceaser suggests, seeking to change the Democratic Party's rules because of an abstract belief in "plebiscitary" democracy. Rather they sought more orderly instruments for change in leadership and policy than the creation of ineffectual third parties or the bloody confrontations in the streets of Chicago.

The war in Vietnam - whose continuation was opposed by the majority of Americans and a sizable majority of Democrats by mid-1968, whose continuation was supported by the leadership of both major parties and which led directly to the demand for reform - is not mentioned once in Ceaser's book.

None of which is to suggest that the proliferation of primaries is healthy for democracy, although it should be readily apparent that rolling back the number of primaries will not, itself, cur what ails either American politics or the American political party.

All of which, however, does suggest that Ceaser is a better political historian than a present social critic.

If one can avoid reading the first half of his overly long introduction and the last chapter and conclusion, which contain inadequate description of and prescription for the American political present - roughly one-third of the book - the rest is well worth having and reading.