What if they gave an election and nobody came? Coloradans may find out soon.

With interest here centered on record spring snows and a lively mayor's race, the contest to fill the vacant seat in Colorado's 6th Congressional District is being run under a virtual news blackout.

So little has been said about the race that when the Republican Party conducted a poll of the district several weeks ago it found that an astonishing 70 percent of those surveyed didn't know an election was coming up, and only 10 percent could identify March 29 as the day of balloting.

As a result, the election has become a testing ground for the techniques of modern-day politics rather than a clash over issues.

The special election was called to fill the vacancy created when newly elected Republican Rep. John L. (Jack) Swigert, a former astronaut and local hero, died of cancer in December.

The Republicans picked state Sen. Dan Schaefer, 47, a well-liked moderate who became the darling of the party's conservative wing at a messy nominating convention. Two weeks later, Democrats nominated Aurora City Councilman Steve Hogan, 34, who got just 37 percent of the vote in losing to Swigert last fall. Hogan played Hamlet just well enough to get a promise that supporters would help erase the debt he had accumulated running against Swigert.

The 6th District is a new, U-shaped district carved out of the Denver suburbs. Republican registration is significantly higher than Democratic, while independents top the registration levels of both parties.

"It's a swing district, but, given enough information, the people here are disposed to vote Republican," one GOP official said.

That makes Schaefer the favorite to keep the seat in the Republican column, but Hogan started the brief race with several advantages. The first was that about twice as many people in the district knew him as knew Schaefer; the second was his organization from the fall campaign.

Hogan calls for the elimination of the third year of President Reagan's tax cut and of tax indexing. He says he wants to cut the growth of the defense budget before cutting domestic programs and, in part because of a sizable block of federal employes in the district, has come out against the Social Security compromise, which will put federal workers on the rolls.

Schaefer is a committed supporter of Reagan's tax cuts and of supply-side economics.

"If that theory hasn't brought down inflation and interest rates, what has?" he asks.

The Reagan administration's problems with the Environmental Protection Agency also could spill over into the special election because of a controversial chemical waste dump in the district. It has been closed, and Schaefer says in his ads that he has fought to keep it that way.

But Hogan points out that Schaefer once voted against a resolution in the Colorado Legislature that would have encouraged the EPA to close it.

But none of these issues seems to have attracted much attention, and as a result the contest here is quite simply one of resources.

Every Republican and independent in the district will get six pieces of direct-mail literature from Schaefer before the campaign is over, and he is spending at least $60,000 to raise his name identification.