Washington — Jesse Helms's mail this week brought something that gave the conservative North Carolina senator a sort of grim pleasure: three brand-new paintbrushes. Senator Helms promptly put the brushes in his briefcase so he could show them to friends and colleagues.
The brushes were a reference to Helms's angry remark after a Soviet fighter shot down Korean Air Lines Flight 007. That outrageous act, Helms growled, is a perfect chance to ''paint'' the Soviets ''into a corner.''
The trouble, conservatives say, is that President Reagan refuses to pick up the paintbrush. His actions so far, chides Robert Bartell of Liberty Lobby, have been ''predictable and very weak.''
Says Craig Shirley of the National Conservative Political Action Committee: ''There are people here who have worshipped at the altar of Ronald Reagan for 20 years, and they feel betrayed.''
Publicly, Mr. Reagan has talked tough. He has spoken of the Soviet ''massacre'' of 269 people. He has called it a ''crime against humanity.'' But in private, the President has warned his staff against US ''overreaction.''
Retaliation by the United States has been limited to a few guarded steps: closing Aeroflot offices; calling for other nations to suspend commercial flights to the USSR for 60 days; halting talks with the Soviets on a few minor topics.
Conservatives don't plan to leave it there.
''It's not going to go away,'' a Helms aide warns.
As a first step, conservatives sponsored an amendment to toughen a joint congressional resolution that condemns the Soviet Union's ''crime.'' They urged Reagan to:
* Recall the US ambassador from Moscow for urgent talks.
* Expel 125 Soviet diplomats.
* Urgently reassess the full range of US-Soviet relations, including arms control, human rights, and trade.
* Report to Congress on whether the Soviets are abiding by earlier arms control agreements.
* Link success at arms control talks to Soviet willingness to abide by international law - with emphasis on the 007 flight, the Helsinki accords, Afghanistan, Poland, and the use of chemical and biological weapons.
* Emphasize the inconsistency of Soviet military forces in the Americas with the Monroe Doctrine.
* Tighten export controls on high-tech items.
* Prevent imports of Soviet products unless the president certifies that they were produced without using forced labor.
In addition to such specific anti-Soviet steps, conservatives say they hope that Flight 007 has created a new atmosphere of skepticism about relations with the USSR.
If it has, they say, Congress and the White House may look at a wide range of issues from a new perspective - issues that range from ''foreign aid'' to ''support for Nicaraguan freedom fighters.''
''This has, we think, created a new attitude in America,'' says a conservative staff member on Capitol Hill. ''The Soviets melted the nuclear freeze movement in about 30 milliseconds (when they shot down the airliner). Our hope now is that as foreign policy issues come up in the future, the lessons learned from 007 will be applied to all these areas.''
The White House has been cool to such suggestions. And that raises the possibility that conservatives might step up the pressure on Reagan as the 1984 election nears.
There has already been some rumbling on the right. Officials of the National Conservative Political Action Committee (NCPAC) have suggested that financial support for Reagan's reelection could be withdrawn.
Says NCPAC's Mr. Shirley: ''Reagan is the most conservative president since Franklin Roosevelt. But today Reagan is moving away from his base of support.
''In 1980, conservatives were working 24 hours a day, seven days a week for Reagan. This time they may not be so enthusiastic.''
NCPAC has already spent $1.5 million toward Reagan's reelection, and is pledged to raise $5 million toward that goal. But the organization has now scheduled a meeting for Oct. 5 to decide whether to abandon that goal, and turn its effort toward other races.
''(NCPAC's director) Terry Dolan feels personally betrayed,'' Shirley says. ''I've never seen him so frustrated.''
There is no doubt that conservative frustration with Reagan also stems from earlier positions he has taken. They have seen much of their agenda - on abortion, school prayer, balanced budgets, education, and other areas - sidetracked.
Flight 007 was merely the last straw. As Shirley of NCPAC says:
''Conservatives consoled themselves that even though Reagan's head was turned by pragmatists on social and economic issues, they still had a strong anticommunist in the White House.'' Now, he says, Reagan is even a disappointment on that issue.