AH, THE SOLACE of a second debate: President Reagan now knows that his four-year string of verbal inanities isn't going to deflate his cozy 15-point advantage. This battle really is over. Hail to our doting, yet avuncular Chief.

Republicans have finally dusted, off that nuisance, Mondale, and they can now turn their attention elsewhere. And the result of this contest will, in all probability, determine the efficacy of Reagan's second administration. Most analysts believe that only the currently Democrat-controlled House of Representatives stands between the President and an effusive outpouring of conservative legislation.

The most salient question of the campaign now becomes, then: is this obstacle destructible? Can the Republicans regain control of the House?

The numbers suggest, quite emphatically, that they will not. In the House, Democrats powerfully outnumber Republicans 266 to 167. And no one is predicting that Republicans can mop up the 50 seats needed to compose a working majority.

For the days of F.D.R. and Truman are gone. In 1932, 97 freshmen rode in on Roosevelt's coattails, and in 1948, 75 Dems latched on to Truman's. But today, the powers of incumbency are too great; direct mailing and casework are simply too effective. In addition, ticket-splitting is increasingly in vogue among voters, and a Presidential ballot does not affect the Congressional one to the impressive degree that it once did.

But the 99-seat gap between the two parties is deceptive because it masks the Republicans' true brawn, for it does not account for the swarm of vouthern Democrats--most of whom are far more conservative than Republican moderates--which has undermined partisan solidarity within the House. Given the ideological similarity between these deviant Democrats and the GOP. Republican strategists would be as pleased as punch to nab just 25 to 30 seats on the other side of the aisle. Such a transfer of power, all agree, would greatly facilitate the initiation of Reagan's agenda, whatever that agenda turns out to be.

In fact, many pollsters and political consultants have been bold enough to predict a transfer of 25 to 30 seats to the Republicans. One Washington analyst even envisions a scenario in which the GOP could pick up 37 seats.

"The clues are there that would substantiate a claim for substantial Republican gains," says Charlie Cook, editor and publisher of the National Political Review.

Most of the factors contributing to the halycon Republican forcast are demographically oriented Presently, the electorate is undergoing powerful transformations, and these changes tend to bolster the GOP's political stamina

Nationwide, more and more voters are identifying themselves as Republican. According to Market Opinion Research, a Detroit-based polling firm, only a bare 46 percent plurality of the voters now (September 43-22, 1984) think of themselves as Democrats, as opposed to 45 percent Republicans. In September 1980, a more commanding 53 to 40 percent majority of the electorate identified itself as Democratic.

Additional polling information also indicates that the nameless Republican congressional candidate has grown significantly more attractive to the voters. Four years ago, a 50 to 39 percent majority of the voters went Democratic in the congressional elections. Today, while the liberals still hold a thin plurality, that margin has decreased from 11 to three points (47 to 44 percent). Moreover, in 1980, despite the generic Democratic candidate's advantage, the GOP nevertheless steamrolled its way to an over whelming 34 House seats.

And from July to September, Reagan's name increasingly carried more weight with the voters. Growing numbers of them who supported the nameless Democrat ironically declared that it's important to give Reagan the numbers he needs in Congress to push through his policies. Much of the electorate, then, is limp, easily swayed into joining the Republican camp when the President is mentioned.

Bad news from the pollsters? Well, there's more. The Republican National Congressional Committee claims to have rounded up more than two million new voters, enough to counter Jesse Jackson's registration efforts in the south.

And, there's a whole slew of weak Democrats drowning in strong Republican districts: New York's Stanley Lundine is said by many to be gone, and California Dem Jerry Patterson is having a hard time keeping his head above water. To this list add James McClure Clark, Don Albosta, Bob Carr, Tim Penny and Joe Minish. All of these Democrats are ideologically off base in their respective districts.

IS THERE ANY hope at all for liberals? Or will they spend the next four years worrying about further budget slashes and additional legislation that dicates the way to