COULD 1984 BE a Democratic year in disguise? Let's toy with the conventional wisdom here for a moment, just for fun.

The subject is not the presidential contest. Yes, miracles can happen, but they are strictly rationed, and this doesn't seem like a miraculous moment. President Reagan does appear to be the people's choice; let's grant him a big victory on Nov. 6.

But where are his coattails? Nine days before the voting, they are not in evidence. Democrats today expect to pick up a seat or two or three in the Senate, and to lose only a handful in the House. Republicans make no claim that they will win an appreciable number of new congressional seats.

The Reagan campaign has abandoned the idea of using the president's personal popularity to help Republican congressional candidates. There are two races for House seats in Connecticut, for example, where Republicans ought to have a chance to beat incumbent Democrats, but when Reagan went to Connecticut on Friday, he chose to appear in an area (Fairfield County, the upscale New York City suburb) where the Republican House incumbent, Stewart B. McKinney, is a shoo-in.

The two Democrats who might be vulnerable in Connecticut, Reps. William R. Ratchford of Waterbury and Bruce A. Morrison of New Haven, both said in interviews on the telephone Friday that they felt confident of victory. Both indicated that they expected Reagan to carry their districts easily, and both expressed anxiety that the voting machine lever in Connecticut that allows voters to cast a straight party-line ballot might still block their re-elections. But neither seemed really concerned. More important, each said Democratic issues and their Democratic Party identification were both helping them.

"The Republican Party as an institution is really no place in all of this," said Morrison. He said many Republican candidates "are running away from the platform (adopted at the GOP convention in Dallas) as fast as they can."

"I don't think the Democratic Party and its candidates are in that much trouble," Morrison said. "I don't see the Republican Party as the problem. I see Ronald Reagan as the problem . . . . He's sui generis."

Earlier in the campaign Reagan appeared in Waterbury, where he claimed the mantle of John F. Kennedy as his own. But Ratchford is similarly confident that he can overcome any Reagan factor. "There's a tremendous response (to me) personally," he said.

Is it possible that Ronald Reagan is going to serve a two-term presidency that does no lasting good for the GOP? Yes it is. It seems more and more likely that Reagan's personalized presidency will come to resemble Dwight D. Eisenhower's -- which ushered in eight years of Democratic rule.

Joe Rothstein is a political consultant who has been making commercials for and giving advice to Democratic candidates since 1972. "It's fun to be a Democrat this year," Rothstein said enthusiastically last week. He was particularly excited about his candidate for the Senate in Iowa, Rep. Tom Harkin, who has opened up a big lead over the Republican incumbent, Sen. Roger Jepsen, in the latest opinion polls.

Harkin has portrayed Jepsen as "Red Ink Roger," demonstrating that Jepsen voted to appropriate more money in the last six years than did any other senator in Iowa history, and more than Harkin voted for as a member of the House in the same six years. "There's absolutely nothing in the Republican playbook that says what you do when you've been accused of being a big spender," Rothstein said last week with a chortle.

"Ronald Reagan has buried the three big negatives that Democrats have faced since I got into this business," he went on. In every election except the Watergate year of 1974, he explained, Democratic candidates have been vulnerable to charges that they were big spenders, favored excessive regulation of business and were weak on defense.

"This year Democrats are not seen as the big spenders," he said. "The issue of overcontrol of business has gone away. People by overwhelming margins feel the Defense Department is wasting a lot of money. People feel the deficit is too high, and (that it's) not the Democrats' fault."

Rothstein is considerably more optimistic than many other Democrats, some of whom think the "tax issue" as President Reagan has framed it is considerably more potent than any of the others, especially with swing voters. (Asked what Harkin is saying about taxes, Rothstein replied: "Taxes? Not a word.") But many Democrats agree that they can make good use of the issues this year.

One is Rep. Timothy Wirth (D-Colo.), who enjoys a huge lead in recent polls of his suburban Denver district. Polls of his constituents, Wirth said, show that by far the most important issues are the deficit and the arms race. "People are really outraged by big defense expenditures," he said, acknowledging that he was talking about Colorado voters who favor Reagan 2-1 over Mondale.

In a series of interviews, other Democratic incumbents argued that most of the issues cut in their favor. They said their experience confirms poll findings that a majority of voters is more likely to be on the Democratic side of major issues than on the Republican side.

But there's a problem with this kind of analysis. It assumes that voters actually chose candidates because of their stands on issues. In a year when we seem to be watching the country move decisively behind a personally popular president whose policies are not strongly supported, there is good reason to wonder how much issues really matter.

As usual, few Democratic candidates are concentrating on big national and international issues. A few hours looking at the campaign commercials of some Democratic candidates for the House and Senate provides compelling evidence that most of them are much more worried about their personal images.

Congressional candidates' television commercials are revealing because for most of them, they represent the single biggest expenditure of funds in their campaigns. Rep. Morrison of Connecticut has brilliant commercials on the air this fall, but they are devoted to endorsements from his own constituents. A series of residents of New Haven recount stories of what Bruce Morrison has done for them personally -- not on big issues of state, but by finding lost social security checks, or installing a mail box in an old folks' home. Rep. Wirth's mother tells viewers about his deep roots in Colorado.

M many commercials knock the opposition but offer little in the way of an affirmative message. Rep. Paul Simon of Illinois, a Democrat challenging Republican incumbent Charles Percy, has relied almost entirely on commercials knocking Percy as a flip-flopper. "Where will Charles Percy stand tomorrow?" asks one. "Only his pollster knows for sure."

American politics is now amazingly fragmented. Few candidates for either party present a coherent set of ideas and ask the voters to endorse them. Indeed, what voter can believe that if he votes for Smith, Smith will do A, B and C; but if he votes for Jones, Jones will do D, E and F? No, we don't have a common agenda of ABCs or DEFs. Our congressional candidates run as individuals, freelancers who ask us to like and trust them and to share their general approach to things, not their well-considered view of the world (if they even have one).

At the same time, the issues themselves have gotten so complicated that many voters have given up trying to deal with them concretely. "People don't follow things very closely," observed Rep. Simon, "so if one guy says he's going to cut your taxes, and the other guy is going to raise your taxes, you send to go with the first guy."

The Simon-Percy race provides an interesting window on the politics of 1984. If the Democrats really had a big advantage on the issues, Simon would be ahead of Percy. Arguably, if the race was a genuine personality contest, Simon would also be ahead. Among their colleagues in the House and Senate and among congressional staff members and reporters who cover Congress, the two men are easily separated: Simon enjoys a good reputation as a hard-working, intelligent legislator with an impressive record of accomplishment; Percy is widely and often strongly disliked as a rather pompous posturer who has accomplished surprisingly little in three terms as a senator. But at the moment, Percy -- who nearly lost to a much weaker Democratic candidate six years ago -- is even with Simon or slightly ahead, according to the polls.

Simon is by instinct an unabashed Democrat who fervently believes that government can be good for the country. He likes to solve problems with government programs. He even thinks the government ought to employ people who can't find jobs.

In this campaign, Simon isn't exactly hiding his stripes, but he has redesigned them -- reacting to pressure Reagan has applied to Democrats generally, which has moved most of them toward the center. (Democrats will live to thank Reagan for this.) Last Monday you could have seen the 1984 Paul Simon selling himself to the Homewood Chamber of Commerce in suburban Cook County.

He began with the deficit, describing his plan for dealing with it (close "loopholes" and cut defense spending) and lambasting Percy for pretending the red ink "will just go away." Then he noted that Illinois is last in the nation in "return of tax dollars " -- in other words, Illinoisans get less back from their federal taxes than anyone else. Next was effectiveness. Simon read from Time Magazine: "He (Simon) had more of his bills passed this year than any other member of the House. Percy . . . has never pushed through a major bill of his own."

Finally he got to his jobs program, which would make the government an employer of last resort. "We face a choice between paying people to do something, versus paying people to do nothing. Let's move on the problems of our society. For example, let's pay some of the unemployed who can read and write to teach the 23 million adult Americans who are illiterate . . . ."

At his best, Simon is a very effective candidate. He has found a way to sound like a Democrat, but also to sound cautious and responsible. Percy has responded with a blitz of television commercials, including one ad that blanketed the state for two weeks that was a blatant misrepresentation of Simon's deficit reduction plan. The Percy commercial accused the Democrat of wanting to tax the people of Illinois several times more than even Walter F. Mondale had proposed. The ad was wrong but effective, because the image of Democrats as big taxers still helps Republicans -- despite consultant Rothstein's optimism.

Percy's ability to stay even in this race demonstrates an important truth about our politics. His biggest advantages are his senatorial good looks and his familiarity; he's been a prominent figure for a long time. In modern congressional politics, incumbency, name recognition and good appearance count for a great deal. The Democrats similarly have a lot of strong individual candidates, like Wirth and Morrison, who would do well in almost any conceivable circumstances.

Rep. Thomas Downey of Long Island, another strong Democrat who consistently wins big majorities in a Republican district, offers an "enclave theory" of Democratic politics this year. Individual Democrats, for individual reasons, can hold onto their enclaves -- their seats -- but what the Democratic Party needs is "to start to build new coalitions for the future" on the basis of strong new themes that could move the country. "We can't do that this year," he said.

But maybe that can wait. Driving through the suburbs of Chicago last week, Simon was asked what combination of forces could put the Democrats back in contention for national dominance. "Ronald Reagan will give us a lot of help," he replied. "I think the country is in for some rough times in the next four years."

If he has accomplished nothing else, Walter Mondale has left the Democrats in a marvelous position to say "I told you so" when the second Reagan administration runs into trouble at home or abroad. And the odds seem overwhelming now that there will be trouble. We forget too quickly that the magic of Reaganomics contributed mightily to the worst recession in modern times. The president blamed it all on Jimmy Carter, but from Nov. 7 onward, Reagan will no longer have Jimmy Carter to blame for his failings; they'll be all his.

If a second Reagan administration is a triumph, the Republicans will be in fat city. But triumph is unlikely; more probably, 1984 will look, in retrospect, like a good year for the Democrats.