As the story unfolds for Colorado voters, the U.S. Senate race here is just a typical, friendly contest between an irresponsible Democratic big spender who is soft on the Russians and a military-minded Republican foe of the elderly who is somewhere to the right of Genghis Khan.

What started out to be an orderly and fairly high-minded campaign between articulate candidates - Democratic Sen. Floyd K. Haskell and Republican Rep. William Armstrong - has in its late stages become an old-fashioned political war in which truth was the first casualty. The campaign reflects the state's political traditions and a realization on both sides that here is one of the best national opportunities for defeating a Democratic in

All but abandoned now are the well-made and visually attractive "soft" commercials which depicted Haskell as an effective, outgoing populist and Armstrong as a devoted family man with a keen grasp of issues.

Last week in broadcast commercials and a face-to-face debate, Haskell accused orthodox Republican Armstrong of being "on the fringe, a minority of a minority." He said Armstrong opposed legislation to help older Americans, the handicapped and Nicaraguan earthquake victims while favoring big oil. Latin America military dictatorships and authority for the Central Intelligence Agency to commit murder.

Armstrong, giving as good as he gets, has charged orthodox Democrat Haskell with various ethical conflicts, including abuse of franked mail and misuse of his Senate staff. He also said the Haskell opposed tax cuts and spending reductions and consistently voted against weapons systems needed to keep the United States on a par with the Soviet Union.

Pointing a finger at Haskell during debate at the University of Denver last Saturday, Armstrong said: "Inflation is double digit again - and it's caused by Sen. Haskell."

Most of the attacking has been done by Haskell, who is widely perceived as being slightly behind in the race. The senator and his strategists are trying to convert the election from a refeerredum on Haskell to a decision on whether Armstrong is too far to the right for Colorado.

"As far as we're concerned, Armstrong is the issue in the campaign," Haskell said in an interview after the debate.

In an effort to make Armstrong the issue, the Haskell campaign is running a series of television and radio commercials that use highly selective votes to portray the house member as a foe of the elderly, the handicapped and the poor.

"During his six years in Congress, Bill Armstrong has voted 'no' more times on more issues than just about anybody in Congress - really," says a new Haskell radio commercial. It calls Armstrong one of the few congressmen who "doesn't understand" that the nation must prpvide for its elderly.

After hearing the commercials, Armstrong said bluntly that they could cost him the election if not effectively answered. One answer is a counter-commercial that details Armstrong's three votes favoring ectension of the Older Americans Act, gives the page of the Congressional Record on which his most recent vote can be found and says about Haskell: "Sometimes politicians start to get desperate and play a little loose with the truth."

The apparent basis for the Haskell commercial is an Armstrong vote against a higher-cost version of the Older Americans Act which ultimately was rejected by Congress.

While Armstrong and his strategists consider the Democrat's commercial dirty pool, the Republican candidate has made several statements of questionable accuracy about Haskell.

"Taken as a whole, his record does not reflect a proper concern for national defense," Armstrong said in the recent debate. " . . . he has voted not just to cut fat but to terminate important weapons systems."

Among these weapons systems, as Armstrong sees it, is the cruise missile. Haskell said he supports the cruise as an alternative to the B1 bomber which he proudly voted against and describes as a "damn boondoggle."

The senator's record on the cruise is mixed. He voted to delay testing of the missile on one occasion, and to cut a cruise appropriation on another, but three times voted in support of the weapon system. As in the case of Armstrong and the Older Americans Act, the "no" votes have been misrepresented as the totality.

As the gangsters say in "The Godfather, "all the rhetoric and carefully contrived commercials are "nothing personal, just business." In private conversations Haskell and Armstrong display the professional politician's absence of personal animosity coupled with respect for the abilities of the rival campaign.

And while the campaigns and the commercials exaggerate, both candidates are right in pointing out that the Senate race provides a genuine choice of political philosophies.

Haskell, a 62-year-old attorney, is far more in favor of government solutions to problems than is Armstrong, a 41-year-old radio station owner who celebrates free enterprise and has long espoused the kind of tax cuts that were contained in this year's Kemp-Roth proposal.

Polls show Haskell in serious trouble. In an Oct. 1 poll in the Denver Post, he led among all voters by 4 percentage points but trailed among those most likely to vote by 8 points. Armstrong's own poll shows a similar result.

If Haskell does lose, it is likely to be more a reflection of his political personality than of any clear-cut ideological decision by the voters.

While he seems knowledgeable and friendly in private conversation. Haskell in public is a shy, reserved person who lacks the political graces. After six years in office he still is not widely known in many areas of Colorado. While he waited formally for the university debate to begin, Armstrong was shaking hands throughout the room. When Haskell tried to display a first-name familiarity with a television reporter named Betsy Dills, he called her Cindy.

All of this has taken its toll, and Armstrong has other advantages as well. He has a superior campaign organization while Haskell has had to rebuild his campaign after a shakeup last April Armstrong will spend an estimated $950,000, a 9-to-5 advantage over Haskell. And a low voter turnout is predicted, reflecting an absence of the highly emotional ballot issues present it many western states.

These many advantages seem to point to an Armstrong victory, but it can't be taken for granted.

"It's neck and neck and we're going to keep swinging," says Haskell.

On that score, for either candicate, there can be no doubts.