A lot of Democrats are already counting their gains from the 1982 elections and gloating over the results. They are laughing too soon. Democrats stand to do better than most people thought last year at this time, when the speculation was that Ronald Reagan's Republicans might be the first party to pick up seats in both houses of Congress in an off-year election since Franklin Roosevelt's Democrats did it in 1934. But the Democrats are, in my judgment, quite unlikely to pick up the 30 or so House seats that some are predicting.

The reason is suggested by the old political adage: you can't beat somebody with nobody. Voters do not pull straight party levers automatically; they also consider the ability, personal character and specific views of the candidates. A party needs strong candidates to win elections--candidates who know how to raise the $200,000 or so it takes to beat an incumbent congressman, who know how to communicate their views on the major themes or issues that help their candidacies, who are willing to work 18-hour days for months at a stretch without yawning.

Republicans do not always need such strong candidates to capture a Democratic seat. In 1980, the national Republican Party (and friendly political action committees) raised enough money and put together a good enough basic advertising campaign to elect some mediocre and even a couple of poor candidates; and Republicans will almost certainly be able to do the same in 1982. But the Democrats do not have the national money and national issues needed to elect weak candidates. Their candidates have to raise most of their own money and devise their own campaign strategies. Such candidates are the entrepreneurs of our political system, and as supply-side economists are finding out, entrepreneurs do not rise out of the earth automatically.

National Democratic strategists believe that the issues of 1982 will work for their party. But they do not have enough strong candidates to make major gains-- at least not yet. My own estimate is that there are 35 strong Democratic challengers running today for Republican seats. There will certainly be more, particularly where congressional district lines have not be redrawn. But it's getting late: it takes time to raise money and to figure out how to spend it intelligently, and candidates who have not put together a campaign by mid-March will have a hard time winning in November.

The Republicans have not got all that many strong candidates, either; in fact, they are losing them daily as potentially strong challengers decline to contest Democratic districts in the current negative political climate. But Republicans still have the potential of making strong challengers out of comparatively weak candidates by major infusions of cash in September and October. Democrats will have a much harder time doing this.

Thirty-five serious challengers sounds like a lot. But actually it's fewer than the 40 or so serious candidates Democrats had in Republican districts in 1976, 1978 and 1980. The last time the Democrats captured a large number of Republican seats, in 1974, they had, by my count, 97 serious challengers. The Republicans had 82 serious challengers when they made major gains in 1980.

Even when issues work strongly for a party, as they did for Democrats in 1974 and Republicans in 1980, only about 45 percent of its serious challengers win; and even then, between 10 percent and 15 percent of the serious challengers of the other party win, too.

So, assuming that redistricting produces no net gain for either party, if the Democrats have only 35 strong challengers in Republican seats, they are not likely to gain more than 15 House seats--and that is assuming opinion on issues works as strongly for them as it did in 1974. The Democrats' glee is premature--at least until they come up with more strong candidates.