AFTER THE TITANIC Democratic struggle of 1968, one recurring and irrefutable criticism fueled the engine of rules reform: the "unresponsiveness" of the system by which convention delegates were selected. Facts were on the side of the advocates of changes in the party rules. On Nov.30, 1967, when Sen. Eugene McCarthy announced his candidacy, 970 of the 1,312 delegates needed for nomination at the following August's Democratic national convention had already been chosen. Thirty-eight percent of all delegates to the convention had been decided even before Sen. McCarthy decided to run.

So, very few people were surprised when the Democrats announced, among the changes in their delegate-selection rules, the requirement that the entire delegate-selection process be conducted within the calendar year of the convention. That seemed fair enough and was one change that guaranteed little argument or even discussion. After all, who could oppose making the whole nominating process more open, uniform and "responsive"?

Because of some other party rules changes, however, more and more states decided to go to primary elections for choosing conventional delegates. The number of primaries grew from 17 in 1968 to 36 in 1980, and here came a complication. All these primaries were, of course, to be held within the presidential calendar year; but because of new requirements for the democratic selection of delegates for each candidate's slate (e.g., public notice, meetings, etc.), the entire process required a longer lead-time. So on Feb. 26, when New Hampshire officially inaugurates the election year with its traditional "first in the nation" primary, filing deadlines for delegates will have already passed in Alabama, Connecticut, Florida, Georgia, Illinois, Kansas, Massachusetts, North Carolina, Pennsylvania, Puerto Rico, South Carolina and Vermont.

So much for timeliness and openness to last-minute candidates. Any late-starting candidate will not only be fighting the primary calendar, but must also deal with the reality of the public financing law for presidential campaigns. To qualify for matching public funds, the late entrant must raise, like all his competiors, $5,000 in each of 20 states. These contributions must come from individual citizens, and no single contribution can exceed $550. For a candidate without an existing national constituency, this can mean only one thing: the investment of a lot of time and travel. The answer to all of these obstacles imposed by the changes in the party rules and the campaign law is simple: a candidate must start at least a year and a half before New Hampshire to allow time to meet all the filing deadlines and to qualify for matching funds when they do become available in January of the presidential election year.

There is one major problem with the early start and the early filing dates: the system lacks flexibility and -- what else? -- "responsiveness."

That lack is increasingly obvious with the daily reports from Iran and Afghanistan and the growing perception of shifting interests and values in the political world. The two opponents of President Carter within his own party, Sen. Kennedy and Gov. Brown, have records that do not present an alternative to his policy that many Americans might now be looking for. They have been, generally speaking, to his dovish left. What if the altered political picture suggested to Democrats the need for a different kind of challenger-candidate? Could one make it under the new "responsive" system? With all the reforms and improvements in the nominating process since 1968, with all the attempts to instill this "responsiveness," the fact is that in the second week of January -- almost seven months before the Democratic national convention -- it is probably too late for a Democratic candidate who represents a different point of view on foreign policy to enter the race. That's not reform.