On two successive days, two political fund-raising letters, each signed by a Democratic member of the House of Representatives. Both signers have voting records pleasing to the addressee. Both letters are in the English language. Beyond that, resemblances cease.

The shorter of the two is on the letterhead of Rep. Morris K. Udall of Arizona, and it reads as though he may actually have composed it. The first paragraph quotes a poem favored by Robert Kennedy -- not, perhaps, a very good poem, but a poem. Down the page, Udall notes that for the first time in many years he faces opposition in the primary election:

"In January, State Senator Luis Gonzales announced that he would attempt to defeat me for the Democratic nomination. Senator Gonzales is intelligent, vigorous and ambitious. In a far-flung district like the Second Congressional District, there is always the potential for an upset."

Two puzzlers here, one minor (what is a "far-flung district"?), the other a real stunner: What kind of politician describes an opponent as "intelligent" and "vigorous" as preface to asking for campaign money on his own behalf?

The rest of the letter suggests a possible answer: it may be that Mr. Udall is a serious politician. He nowhere implies that his own defeat will imperil the republic; he does point out, mildly, that his seniority in Congress makes it possible for him to work effectively on the issues that concern him. And he names some of those issues, making clear his general stance toward them: acid rain, the disposal of hazardous waste, arms control and the overall tone of U.S.-Soviet relations. The harshest criticism is of Gramm-Rudman-Hollings; it is "well-intended," but "hastily drawn" and "short-sighted." Of fear-mongering there is none; nor is there any imputation of evil motives to political opponents.

The other letter was signed by Rep. Tony Coelho of California in his capacity as chairman of the Democratic Congressional Campaign Committee, but it doesn't sound much like the Coelho one sees on television from time to time. In person he seems thoughtful; his letter sounds frenzied. Of its 43 paragraphs, 18 (41 percent) are either wholly or partially underlined for the sake of emphasis, as in this final paragraph:

Jerry Falwell has said, " . . . it isn't a question of if I win, only when." That's a frightening thought. Please help us prove Jerry Falwell wrong.

Jerry Falwell's name appears in the letter 19 times, along with a great many adjectives. The message is that Falwell and his "powerful," "well-financed," "ultra-conservative" allies are engaged in a "tough and dirty fight," in which they are using the "misleading," "deceptive," "vicious" tactics of "Moral McCarthyism" with the aim of "taking control of America's future." To counter this evil plot, Coelho's committee has launched a "Democratic Candidate Defense Campaign." Recipients of his letter are asked to send money.

But why? What different future for America do the Democratic candidates envision? Deponent sayeth not. Nothing in the DCCC letter suggests that politics has to do with governance as well as electioneering, or that potential contributors to a political party may wish to know how the party differentiates itself from its opposition. Interestingly, Coelho's letter does not mention the name of Ronald Reagan or any of his policies. It refers to George Bush only because the vice president recently paid tribute to Jerry Fallwell.

The question the letter raises is whether the Democratic Party exists. The same question arose when Sen. Jim Sasser, appointed to give the official party response to Reagan's address on Central America, failed to point out the president's frequent misstatements, did not mention the word Contadora, and asserted that "we Democrats" share Reagan's "objectives" in Central America and differ only as to "means."

The two letters drew differing responses. To Udall, a check. To Coelho, a note concluding: " . . . [A]n opposition party does not serve the country well if it does not in fact oppose, and, occasionally, propose. I will reserve my support for candidates who seem willing to take those risks." In retrospect, the check to Udall seems to the sender a mite stingy. Try it again, Mo.