. . . When you advise Chairman Manatt in The Post (op-ed, March 3) against "tinkering with the chassis" of the Democratic Party, that assumes there is a chassis upon which he can work his will as a "nuts-and-bolts" chairman. That's the problem. Manatt has been handed the bill for a nonexistent vehicle we nostalgically refer to as the Democratic Party.

I admit to the bias of the technician, but I can show you the scars of too many battles over the years with Republicans in which we were outdone both financially and technically. I admit that this was the year when we also ran out of ideas and that we must start from scratch to develop the argument that says to the people of this country, "These are the ideas and reasons for returning Democrats to power." We dare not still another patch on FDR's spare tire.

My difference with you, Mr. Rauh, is that, once that argument is developed by the candidates, incumbents and philosophers of our party, we must be able to turn to some central operation that is abreast of the new technology and financially solvent enough to back up our candidates' ideas with the communications system necessary to get that message across.

In the last election most of our candidates were swamped by the financial and communications resources of the Republican National Committee. This is a fact. It is no secret that our national party, on the other hand, was a front organization for the presidential campaign; and thus it has always been.

I remember checking into my new office at the Democratic National Committee as director of radio and TV after the convention of 1968 to find nothing but an empty office with a few bumper stickers supporting an LBJ resurgence. All we had to start with was some expensive office space full of cheap furniture. When we had completed our assignment of running the presidential campaign, we left the party as we found it -- plus the debts of our primary and general election candidates.

Manatt has a chance to reverse this tradition and build a party structure that can give technical support to all of our candidates for public office, from the state legislatures to the highest office in the land, and in so doing build the platform upon which you and all of the other sections and factions of our party can hammer out our new and, we hope, more compelling philosphy of government. That shouldn't be as difficult as it might seem, when you consider that in the last election the most exciting "new idea" from either Democrats or Republicans was labeled "Kemp-Roth."

Finally, in the days of Paul Butler (the chairman you suggest Manatt model himself after), campaign computers did not exist, television was in its infancy and only Franklin D. Roosevelt had figured out how to use radio. Public opinion polling hadn't graduated from the Literary Digest debacle, and direct mail was thought to be the thank-you notes that candidates would strew along behind them in the hope of following up on their personal contacts. It was the era before the "campaign industry" was born.

It is my own observation that the decline of party importance in this country can be directly linked to an inability to master the new technologies of campaigning. Parties used to be central to the communications process between candidates and voters; now they have been short-circuited by the practitioners of the campaign industry.

It is a different world, Mr. Rauh, and Bill Brock (the retiring chairman of the Republican Party) figured it out before we did and did something about it. Given the fact that the Reagan administration didn't know what to do with this obviously talented and successful party chief/mechanic, he was my first choice for Democratic Party chairman. In light of Brock's obvious unavailability, I am delighted that Manatt got the job -- he looks like the kind of man who knows, where the tools are, is willing to pick them up and use them to build this party (I can't even say rebuild) into an entity that is competitive with our opposition. Once he has done that, and you and others like and unlike you have figured out the messages, we hope Manatt will have constructed the vehicle for their transmission -- he might even have raised the money to pay for it.