The 1984 presidential race already promises to be the longest campaign in US history. For the Democrats, the '84 contenders will parade before California's 2,100 state party delegates in Sacramento this weekend. This alone speeds the election's pace by 11 months over the last presidential cycle. The 1980 presidential race was kicked off by a Florida straw poll taken Nov. 17-18, 1979, as the first test of candidate strength.
Straw polls at the California meeting will give the first reading of candidates' potential clout in the race for delegates to the 1984 national convention.
For the Republicans, Tennessee's Sen. Howard H. Baker Jr. has indicated he may drop out of the Senate when his term ends in 1984. Some observers say this is a bold move to position himself for another bid for the White House, if Reagan decides not to run.
Senator Baker's move carries strong implications for President Reagan's rule in Washington. It may also have a bearing on whether the President decides to run for reelection. Baker, as Senate majority leader, has proved essential to Mr. Reagan's leverage on Capitol Hill.
Reagan's refusal to announce his intentions for 1984 is prompting those in the GOP presidential stockyard to move out on their own. Sen. Bob Dole (R) of Kansas, another powerful Senate leader, is seen as using the current budget deficit and social security impasses as a means to portray himself as a national problem solver.
Other factors - from federal campaign finance laws to the AFL-CIO's intention to endorse a candidate eight months before the national convention - also are committing the 1984 contenders to the earliest start ever.
''This will be the longest campaign in modern American history, primarily because of the intended endorsement by labor unions in November or December,'' says Richard Scammon, director of the Elections Research Center in Washington.
Critics of the drawn-out US presidential cycle complain about the party caucus and primary season, which has run from January to June in past election years. But campaigns take on a life of their own, Mr. Scammon says. Attempts to shorten the process, like providing federal campaign funds, wind up lengthening the process. That's because candidates have to organize early to qualify for matching funds.
Already, former Vice-President Walter Mondale, Sen. Alan Cranston of California, and former Florida Gov. Reubin Askew have announced they have qualified for federal matching grants for 1984.
''What creates an early campaign is a campaign,'' Scammon says. ''We're getting ready for a long, long one.''
''The campaign has been speeded up by twice over 1980. With the California convention coming up, now we're going to have an event in the '84 campaign nearly 18 months before the convention meets, instead of eight months last time, '' says Austin Ranney, director of political studies for the American Enterprise Institute. ''The big question on the Republican side is whether Reagan will run again. If he does decide to run again, the standing of the other Republicans won't matter.''
Reagan's awkward approach to the new budget, his exasperation with press leaks that prompted him to clamp a lid this week on media contacts by White House officials, provide a backdrop for the presidential ambitions of Democrats and Republicans alike.
But even without regard to Reagan's immediate troubles, the Republican Party needs backup candidates to prepare for unforeseen circumstances for 1984. Thus prospective GOP candidates like Oregon Sen. Robert Packwood, who is off to New Hampshire this month ostensibly to talk about ''the soul of the Republican Party ,'' must test the waters quickly to be in position for an '84 run.
Meanwhile, voters at this point are at best only broadly involved in the 1984 contest. Polls show Reagan trailing Walter Mondale and Sen. John Glenn (D) of Ohio if the election were held today. But this reflects ''economic discontent'' rather than a comparison of candidates, cautions Ted Van Dyk, executive director of the Center for National Policy, the new Democratic think tank in Washington.
''If the economy turns up in '83 and '84, and if there's no great external event, Reagan is the odds-on favorite,'' he says. ''If the economic comeback doesn't occur, you have to rate any Democrat as the favorite.''
''What counts is not how you rate against Ronald Reagan, but how many committed people you have on the ground in Iowa and New Hampshire,'' Mr. Van Dyk says. The Iowa caucus, set for Feb. 27, 1984, will again start the official delegate drive. The caucus will be followed by New Hampshire's March 6 primary.
The public will likely be firming up its views of the two party's candidates right up to the national conventions. But here are some of the electorate's key perceptions as the '84 race begins:
* If Reagan doesn't run, Vice-President George Bush would be the favorite GOP candidate in the primary with 36 percent of the vote, Baker second with 21 percent, US Rep. Jack Kemp of New York with 7 percent, Senator Dole of Kansas with 6 percent, and Sen. Jesse Helms of North Carolina with 2 percent, according to an extensive survey taken in December by Penn & Schoen Associates for the Garth Analysis, a political analysis publication.
Among Democrats, Mr. Mondale would get 42 percent of the vote, Senator Glenn 18 percent, US Rep. Morris Udall of Arizona 8 percent, Sen. Gary Hart of Colorado 3 percent, Senator Cranston 3 percent, and Sen. Ernest Hollings of South Carolina 1 percent.
* Reagan trails Glenn and Mondale by 6 percent in the Penn & Schoen matchups. This is a somewhat narrower margin than December's Gallup survey, which showed Reagan trailing by more than 10 points. The Penn & Schoen surveys test voter attitudes, not those of the general public.
* The public tends to see candidates other than Reagan as more moderate than their voting records in Congress would indicate. The public puts Mondale just left of center despite his very liberal Senate record. Mondale's style is one of moderation, and as Carter's vice-president he is associated with a centrist Democrat, explains Stephen Winthrop, Garth Analysis's senior editor.
According to the Americans for Democratic Action ratings, based on some 20 key votes in each congressional year for four or more sessions of Congress, here is how the candidates would rank from most liberal to most conservative: Democrats - Mondale 92 percent, Cranston 84, Senator Hart 77, Representative Udall 71, Sen. Dale Bumpers of Arkansas 69, Glenn 64, Senator Hollings 40; Republicans - Senator Packwood 45 percent, Baker 15, Senator Dole 14, Representative Kemp 8, Bush 7, Rep. Philip Crane of Illinois 5, Senator Helms 4.
Eleven percent of the voting public sees Reagan as liberal, 21 percent as moderate, and 60 percent conservative, according to the Garth Analysis. Thirty-one percent label Mondale liberal, 32 percent moderate, and 26 percent conservative. Glenn is rated by 19 percent as liberal, 29 percent as moderate, and 15 percent conservative, with the remainder unsure. The public sees itself as mostly moderate - 45 percent - with 35 percent conservative and 16 percent liberal, in the same Penn & Schoen survey.
''A potential problem for the Democrats involves public opinion regarding the AFL-CIO's plans to endorse a candidate for 1983,'' the Garth Analysis says. ''A majority of the voters (56 percent) feel that such an endorsement is an unfair attempt by the unions to influence the outcome of the elections, while only 25 percent regard it as a good thing. In addition, 24 percent say that such an endorsement would make them less likely to vote for the endorsed candidate.''
Only 15 percent of the public say Mondale's role as Carter's vice-president makes them less likely to vote for him, the Garth Analysis reports. Twenty-five percent say it makes them more likely to vote for him, and 56 percent say it would have no effect. ''Evidently being connected with the former President is not at this point the dead weight that was thought by many political observers, '' the Garth editors conclude. Finally, 55 percent of voters say they don't know much about the Democratic candidates for president, while 42 percent say they do.