Washington — Campaign workers for Sen. Paul S. Sarbanes have a ''scenic'' view as they stuff envelopes in their Baltimore headquarters. Only a few feet away stands a red and white billboard proclaiming ''Paul Sarbanes Too Liberal For Maryland.''
The sign is a reminder that an independent group, the National Conservative Political Action Committee (Nickpack) has poured more than half a million dollars into Maryland attempting to defeat the one-term Democrat. But as election day nears, the effort appears to have failed. Senator Sarbanes holds a big lead over Republican challenger Lawrence J. Hogan.
In fact, the attack on Sarbanes is widely seen as having backfired. It gave him an ''identification,'' says Democratic pollster Peter Hart, and that's useful to a candidate who was fighting a reputation for being colorless.
Only two years ago Nickpack launched an attack that helped to knock out some the Senate's best known liberals and promptly announced it would go after 20 targets in 1982. The hit list has now dwindled to 11, and most of those senators look safe for reelection.
But no matter how the voting turns out next Tuesday, such negative campaigns by independent groups are on the upswing. A report issued by People for the American Way, a new liberal think tank, finds that such groups had already spent a half times the amount for the entire 1980 elections.
Virtually all of this independent money goes into negative campaigning. It has paid for Nickpack's TV ads to paint Sarbanes as a senator who votes for school busing for desegregation (while sending his own children to private school, intones the narrator). The funds also go to publish and mail out thousands of copies of a ''comic book'' satire on Sen. Edward M. Kennedy (D) of Massachusetts, put out by Citizens Organized to Replace Kennedy.
While such groups once confined their activity to Senate races, they have now moved into House contests as well. Nickpack, by far the biggest, has spent money to oppose at least 17 House members this year.
Moreover, while once the game had been confined to New Right, anti-abortion, or conservative groups, new players have now arrived. At least four liberal groups have formed political action committees and launched independent ''negative'' campaigns.
For example, the newly formed Progressive Political Action Committee (PROPAC) is trying to unseat Republican Sen. Harrison Schmitt, the former astronaut from New Mexico. The liberal group has produced an ad showing a man combing his hair in front of a mirror with the caption ''Jack Schmitt may not get much done in the Senate, but he sure looks good doing it.''
The emergence of the negative independent campaign has brought criticism because these groups can distort records and even tell lies, and no candidate is held directly responsible. But the still unsettled question is whether the negative campaign works.
''I think it works,'' says Peter Fenn, executive director of Democrats for the '80s, one of the new independent political groups. Mr. Fenn was campaign manager for former Sen. Frank Church (D) of Idaho, who lost after an anti-Church blitz by outside groups.
''The level of cynicism of voters is quite high, and they're very susceptible to negative attacks,'' Fenn says, comparing the situation to commercial advertising.
A study made by political consultant V. Lance Tarrance Jr. of Houston for a conservative group concludes found that voters reject strictly personal attacks, while they like ''information-gathering'' TV ads that draw sharp differences between candidates.
The study called negative campaigns a ''viable way to create a 'lightning rod' on the incumbent and to force the incumbent to defend his record.''
Victor Kamber, treasurer for PROPAC, calls independent expenditures on campaigns ''horrendous,'' but adds that he helped form PROPAC because it would be ''naive'' for liberals not to counter Nickpack.
According to Mr. Kamber, even if the Nickpack hit list fails to defeat liberals this year, the group has already won victories, since many candidates are now avoiding liberal themes.