Making a monster out of conservative Republican Sen. John Tower is proving difficult for youthful Rep. Robert Krueger and the newly unified Texas Democratic Party.

"Tower's been around a long time," a Democratic courthouse official told us in Karnes County, deep in southern Texas. "He's made enemies and friends, and I reckon there's more friends than enemies."

That sums up the once glittering prospect that Tower, called "the accidental senator" by Lyndon Johnson, would at last be unhorsed. With Tower and Krueger agreeing on most economic and oil-and-gas issues, the glitter foreseen for this campaign has turned to ho-hum boredom, a far greater hazard for Krueger than Tower.

Converting those Tower "friends" into "enemies," at a time when most Texas voters turn off at the word "politics," has moved Rhodes scholar Krueger into public scrutiny of ancient parts of Tower's voting record. He reaches 14 years back, blasting Tower for opposing the 1964 civil-rights bill. But Tower survived that vote in 1966 and 1972, when he was reelected to the seat he first won in 1961.

Likewise, Krueger is trying to exploit what is sometimes called the "morality" issue against Tower. His principal fund-raising committee mailed to newspapers throughout the state a published weekly newspaper column that, without actually naming Tower, stigmatized him as a womanizer. Typed across the top of the mailed column was this message from "Friends of Bob Krueger Committee": "Dear Editor: Thought you might be interested in this unusually candid description of Bob Krueger's opponent in the U.S. Senate race, John Tower."

Krueger himself is more careful. The closest he has come to a frontal attack on Tower's moral fiber was to describe him on Oct. 11 as "one of Tongsun Park's closet friends" in a pep talk to courthouse politicians and a few voters in the southern Texas hamlet of Goliad. He coupled that with a reference to former representative Wayne Hays's sexual shenanigans which, he said, discredited Congress.

Tower's camp is equally adept at sleazy tactics, raising oblique questions about the fact that Krueger has never been in military uniform and, at 43, is unmarried.

That is grist for the political gossip mill, but scarcely the transcendant stuff that makes for an electrifying Senate campaign. Indeed, with two candidates, who agree on so much, neutralizing the tax-and-spending issue, the Tower-Krueger battle is more shadow-boxing than blood and thunder. The campaign was ummed up by one astute Democrat: "I can't remember a single thing either one of them has said so far."

For Tower, an invisible campaign is golden. He alarmed his managers in mid-summer by paying little attention to waht is by far the most serious challenge he has ever faced. While TOwer stayed in Washington, Krueger risked the charge of missing roll-call votes in the House to make himself known across this vast state. But while building momentum, he failed to build a single issue to turn voters against Tower.

Evidence of the Krueger stall is found in scarce campaign funds for high-cost media ads over the campaign's final three weeks and indications that the big voter turnout planned as the campaign bedrock may not materialize. Krueger's campaign was budgeted at close to $2 million, far more than he has collected.

To overcome voter boredom, particularly in the large Mexican American minority, some Krueger operatives wanted Sen. Edward M. Kennedy for a swing through south Texas and the Rio Grande Valley. But Kennedy had no time. Instead, he has cut media tapes in Spanish, exhorting a big turnout. Such arm's-length exhortation is questionable at best.

Further demonstrating Krueger's need of Mexican American support was the Oct. 12 charge by Luis de Leon, Senate candidate of the left-wing Raza Unida (Race United) Party, that he has been under Democratic Party pressure to get out of the race.

Tower is perceived by some Democrats as an odd but not uncomfortable piece of furniture that somehow got moved into the family parlor and isn't worth the effort to move out. His campaign is individualistic and divorced from all other Republican candidtes, particularly the volatile campaign of former deputy defense secretary William Clements, running for governor against state Attorney General John Hill.

Fearful that Clements's tough, hard-hitting strategy could heighten voter turnout, Tower has banned all Clements campaign literature from his own campaign. He has ignored superstars Ronald Reagan and Gerald Ford, who have come here for Clements.

Tower thinks that if the voters don't turn on and turn out, he can quietly cash in 17 years of political chits and stay in the Democrats' parlor, and he is probably right.