Washington — Look beyond Super Tuesday and Super Saturday. Look beyond all the other primaries and caucuses. Look all the way to July when the Democrats meet to select their nominee, and adopt a platform.
Then think about Jesse Jackson.
As this campaign unfolds, Mr. Jackson has been spelling out his ''agenda'' for the party. He demands a woman nominee as vice-president, tougher enforcement of civil rights laws, and an end to runoff elections where blacks have a harder time winning.
Some of this will be easily incorporated into the Democratic campaign. But other parts of it will be difficult for the party to swallow.
Some Democrats wonder what Jackson will do if his agenda is ignored by the party - or if only part of it is found acceptable. Will he boycott the convention? Will he urge blacks to stay at home on Election Day?
The answer to those questions could be vital to Democratic Party hopes against President Reagan. No matter who the Democratic nominee is, there is little doubt that without almost solid black support, he cannot get elected.
To a large measure, that means Democrats will strive to keep black leaders like Jackson happy.
One of the most difficult demands that Jackson has made relates to second primaries. He suggests that any candidate who won't support an end to second primaries could hardly expect his support in the fall.
Second primaries are also called runoff elections. They are widely used in the South, and also are occasionally in use in other parts of the country.
The logic of a second primary is obvious. It is meant to ensure majority rule.
In the South, where the Democratic Party has been dominant during this century, the nomination of a Democratic candidate for governor, for example, has usually been tantamount to election. The Republican nominee seldom has a chance.
However, five, 10, or even more candidates may run in a state like Georgia for the Democratic nomination. This means that the person who comes in first could have as little as 15 or 20 percent of the vote.
Thus the need for a runoff. In the runoff, the first and second place winners are matched against each other, and the winner gets the Democratic nomination.
The same system is used for offices up and down the political ladder, from governor to dog catcher.
Jackson, however, says the system discriminates against blacks. More and more blacks are running for office in the South. Quite often, black candidates come in first in the initial vote. But Jackson says that in the runoff, white voters act as a bloc, and support the white candidate. So the black candidate who finished first in the initial vote, loses in the runoff.
Jackson now has filed suit in the US District Court in the Northern District of Mississippi. He wants the court to declare that second primaries are illegal.
In his suit, Jackson cites several cases, including that of Malcolm Walls, who ran this month for Washington County (Miss.) chancery clerk. Mr. Walls won the first primary with a plurality in a field of 10 candidates. In the runoff, he lost to a white opponent.
James Sunquist, an analyst with the Brookings Institution in Washington, says Jackson's challenge to second primaries raises complicated issues.
It represents, Mr. Sunquist notes, a ''clash of values.'' On the one hand, getting more blacks elected is seen as a worthy goal. But majority rule is basic to a republican form of government. To claim that someone should be elected with less than 50 percent of the vote violates the most fundamental principles of democracy.
Recent history, in fact, shows that runoff elections are not always bad from a civil rights standpoint. The picture is mixed.
In 1974, Lester Maddox, a segregationist, won the first primary in the Georgia governor's race with 35 percent of the vote. George Busbee, a moderate on civil rights, came in second with 22 percent in a 12-man field. In the runoff , Mr. Busbee won with 60 percent. Georgia blacks were delighted.
In 1973, Tom Bradley, who is black, went up against Sam Yorty, who is white, in a runoff election for mayor of Los Angeles. Mr. Bradley won with 56 percent of the vote, even though the city was only 18 percent black. Mayor Bradley is now in his third term - a record for that city. Says Bradley: ''People will listen to a candidate and make their judgment on merit instead of race.''
In 1983, Harold Washington, a black, came in first with 36 percent of the vote in the Democratic race for mayor of Chicago. That city has no runoff. The white vote was split between Mayor Jane Byrne and Richard M. Daley Jr., son of the former mayor. Mr. Washington might well have been beaten in a runoff. Instead, he became the city's first black mayor.