HAVE YOU HEARD the latest Conventional Wisdom? The economy is coming back, so Ronald Reagan is a heavy favorite to win reelection next year. The Democrats are in total disarray; they haven't got anybody who could stand up to the Great Communicator. Fritz Mondale? Hah.

Washington loves Conventional Wisdom. In this town original thinking is generally treated as a form of venereal disease. Players in Washington rarely want to figure out a big issue. Instead, they want to know who is on what side of the issue, so they know where they should be themselves. So various versions of the Conventional Wisdom become guideposts to the entire community.

The current CW is broadly shared (by definition, it has to be). A lot of Democrats are singing it along with Republicans. Curiously, though, it is much stronger on Capitol Hill than in the White House. Some of the president's intimates have been heard making nervous wisecracks about where they'll find a job in January 1985. The president's advisors are pondering how they can win back enough women and blue-collar voters to put together a winning coalition in '84.

As usual, the current version of the CW carries a set of implicit assumptions. One is that the Democrats' failure to come up with an appealing new face for '84 spells doom; the retreads running after the Democratic nomination are "boring," and won't make an impression on the voters.

A second assumption -- not universally shared, but widespread -- is based on classical Washington condescension toward the rest of the country. We in the capital may realize that Ronald Reagan has a weaker grasp of big issues of state than any modern president; we know he has the weakest cabinet in many administrations; we know how anxious are many people, including White House insiders, about what this president who reads little and cares little for intellectual problems might do in a difficult crisis. We smart insiders know all that, but how can the boobs in the hinterlands ever catch on?

If you discuss Ronald Reagan with a dozen or so of the political professionals in this town, you learn that he is actually a very vulnerable incumbent, if only theoretically. His position looks a lot like Richard Nixon's toward the end of his first term. If Nixon had been forced to run against himself in 1972, he might not have won; luckily for him, he got George McGovern instead.

Reagan's weaknesses are considerable. According to Patrick Caddell, the Democratic pollster, he is the first modern president to fall behind leading rivals from the opposition party in trial heats run by pollsters in the second year of his presidency. (Mondale beat Reagan in such trial heats in polls for much of last year). By contrast, in May, 1979, Jimmy Carter led Reagan and Gerald Ford in polls by nearly 2-to-1.

Members of the president's political inner circle are less alarmed by trial heats than by the attitudes of particular groups, especially women and blacks. The political fever that appears to be raging in America's black community is a whole new factor in national politics, one no prognosticator can yet assess.

Richard Wirthlin, President Reagan's pollster, noted that an unexpected turnout of black voters elected Chuck Robb governor of Virginia in 1981, and -- more strikingly -- almost defeated incumbent Gov. Richard Thornburgh in Pennsylvania last November, though blacks had no specific quarrel with Thornburgh. Assuming the outcome in 1984 is much closer than in 1980 (this assumption is part of the Conventional Wisdom), a surge of black registration and voting that is 90 percent or more anti-Reagan can have a devastating impact. Specifically, black votes can take both the South and northern industrial states away from the Republican ticket.

On a smaller scale, Jewish votes can also be decisive in a few key states like New York, New Jersey, Illinois and California. Reagan has lost considerable ground among Jews since 1980, when he won 39 percent of the Jewish vote -- and won all those states.

The "gender gap" that emerged during the 1980 campaign -- 46 percent of women voted for Reagan last time, compared to 54 percent of men -- has remained intact. Women's opposition to Reagan is made more serious by the fact that more and more women are voting. Most voters in 1984 will be women.

Reagan has created hard-core opposition among environmentalists. Voters whose principal worry is Social Security are likely to vote for a Democrat. The president has contributed mightily to the creation of an American "peace movement" which, if it survives until 1984, could be a source of serious opposition to him. And the "fairness" issue, so potent in 1982, remains a formidable weapon. ("It's our achilles heel," says one Reagan intimate.)

On most major issues, Americans disagree with the positions taken by President Reagan. The latest Washington Post-ABC Poll, which showed a sharp recovery in Reagan's overall approval rating (his handling of the presidency is now approved by 53-42), also contained evidence that most people disapprove of Reagan's defense budget, his cuts of social programs and his Central American policy. Earlier polls showed in more specific detail how majorities oppose Reagan on the "social issues," domestic economic issues and "war and peace" issues. This is fertile ground for a Democrat in 1984.

Reagan also has a penchant for making impolitic decisions. As John Glenn quipped at the Gridiron Dinner in March, "I have to wonder about an administration that wants to sell Yellowstone Park and buy Times Beach, Mo." You also might wonder about a White House that allows a distinguished political operative like Drew Lewis to leave the cabinet, but clings to liabilities like Raymond Donovan and James Watt.

Perhaps most ominous to Reagan is the danger that the boobs in the hinterlands (who are anything but boobs) will figure him out -- that he catches the curse of "incompetence." This one is lurking around Washington, but will it ever become a national phenomenon? The president's handlers say there is no evidence of national doubts about Reagan's competence; Caddell says his polls show otherwise. A lot depends on the news media, and so far they have not shown much inclination to go after Reagan on this dicey ground.

James Reston has written a strong column saying, in effect, that the country cannot afford a second term of Reagan's bumbling approach to foreign policy. Other commentators have written harshly of Reagan's disregard for accurate information. People have heard that Reagan is no Rhodes Scholar, but so far the public seems willing to go along with him.

Perhaps that's because people like him so well. More likely, it reflects the messages they're getting. Reagan's is the best-staged presidency in our history; almost nightly he appears on television in some presidential role that suggests he's actively on the job. The public hasn't been told much about the fact that this president does less actual work than any of his modern predecessors. Little has been written or broadcast about Reagan's essential disinterest in so much of what comes before him. When he goofs, he is still likely to get the benefit of the doubt.

When the president gave an interview to six White House correspondents that brought laughter to the White House press room when it was piped there from the Oval Office earlier this month, only Lou Cannon of The Washington Post reported the event in gruesome detail. Most White House correspondents wrote about the interview as though nothing untoward had happened, though it was apparently well understood in the press room that the president's performance had been riddled with errors and confusing statements.

Reagan does get a gentle press. That fellow who can stick his thumbs in his ears and stick his tongue out at the news business -- as Reagan did at the White House photographers' dinner last week -- is so darned nice that no one likes to pick on him.

But this can change, and if it does, it is likely to change with a vengeance. Being a little bit incompetent is the political equivalent of being a little bit pregnant.

Hold the phone. Reagan may be vulnerable, but he is far from beaten. He has a great many political assets still, including many that Jimmy Carter didn't have in May 1979.

His best asset may well be his opponents. It's terribly important for Fritz Mondale that today's Conventional Wisdom includes the belief that Mondale just doesn't have what it takes to win the presidency. Whether accurate or not, this belief is devastating for Mondale's credibility, and to get anywhere in '84, he is going to have to refute it decisively.

Glenn does well in the polls, but Washington's Democratic insiders predict with surprising unanimity that he'll be the George Romney of this campaign. The rest of the field stirs no emotions. If a plausible Democrat doesn't catch fire, Ronald Reagan doesn't have any problems.

Reagan has positive advantages too -- it's hard to fault the CW on this score. A strong economic recovery would help him immensely. His stubborn support for principles he believes in has convinced the public that he is a leader, a great political asset. Although it is bitterly divided on some issues, Reagan's staff is excellent, and has repeatedly rallied 'round to get him out of trouble. Columnist Mark Shields notes that Reagan is the first sitting president since Ike who won't face a primary challenge from inside his own party. The GOP may be on the verge of flying apart, but as long as Ronald Reagan is at its helm, it is destined to be strong and unified.

Up to now Reagan has routed the Democrats in every serious contest by utterly dominating public debate and keeping them on the defensive. Obviously most Democrats are afraid of him, and if that continues, he'll win easily in '84. His essential likeability and his extraordinary good luck may be more than enough to reelect him, especially if the nation decides it isn't prepared to get very excited about presidential politics in 1984. Reagan's presidential style may not suit Washington's frenetic pace, but it just may suit the country.

Hold the phone again. There's a wise Republican senator who ponders the Conventional Wisdom for a moment and says hey, this idea that Reagan has it made is just the excuse he needs to announce that he's not running again. Now that he can retire without appearing to be running from defeat -- now that he can claim the biggest part of his job is done -- perhaps he'll just chuck it in and return to California.

The problem with Conventional Wisdom about future events is its irrelevance. We may wallow in it in Washington, but that doesn't make it important.

Pat Caddell observes that from 1963 until today, anyone who bet the store against the prevailing Conventional Wisdom two Mays before election day would have cleaned up. "You could have retired on your winnings," as Caddell put it. Since the Kennedy administration events have always intervened to nullify all predictions made this far in advance.