RALEIGH, N.C. (AP) _ The two Democrats locked in a runoff for the U.S. Senate nomination are going easy on each other and aiming their fire instead at potential Republican opponent Sen. Jesse Helms.

Democrats Mike Easley and Harvey Gantt have carefully avoided attacking each other during the first two weeks of the runoff campaign. But they frequently jabbed at Helms.

''They have a lot of common supporters and it's hard to insult people who are fairly close to you,'' said Thad Beyle, a political science professor at the University of North Carolina at Chapel Hill.

Beyle characterized it as a ''gentlemanly'' runoff designed in part to avoid alienating voters who could choose to sit out the November general election.

Easley is the Brunswick County district attorney, and Gantt is a former Charlotte mayor who is hoping to become the state's first black Senate nominee this century.

Meanwhile, Helms, a three-term incumbent with a nationwide network of conservative financial contributors and supporters, says he isn't taking re- election for granted.

''I hear far too often, 'Jesse's got it made,''' Helms said at one weekend campaign appearance. ''Well, Jesse ain't got it made.''

The state's political history favors Easley in the June 5 Democratic runoff, even though Gantt outpolled him by 50,000 votes in the six-way May 8 primary.

Black candidates such as Gantt traditionally have lost runoffs against a single white candidate after leading a field of several whites in the first primary, Beyle said.

That history led minorities last year to successfully push for a change in state election law that allows a candidate to win a primary with 40 percent of the vote, rather than the old standard of 50 percent. Black voters account for 26 percent of registered Democrats in North Carolina.

While the change in election law was expected to help Gantt, he fell short of the new threshold and finished the primary with 37.5 percent. Easley was second with 30.2 percent. Three other white candidates and one black candidate were eliminated.

Easley, during a weekend campaign appearance, said Democrats should ''focus on the issues and make (Helms') record an issue. We've never done that; we've always got caught up in national politics and that's a mistake.''

Gantt, meanwhile, criticized Helms' vote last week against a spending bill designed to help cities and states cope with growing numbers of AIDS cases. Helms charged that money was being diverted from other diseases and that the bill would encourage homosexual practices, which he termed immoral.

''I thought he embarrassed the people of North Carolina by showing no compassion for the AIDS victims in our society, for showing a lack of understanding as to what in fact has caused that problem to exist,'' Gantt said.

''I just thought it was an embarrassing performance and another example of how irrelevant he is to the times we live in,'' Gantt added.

Both Democrats have been scrambling to raise money while Helms has raised and spent more than $5 million so far. Easley had raised $481,000 and Gantt had raised $402,000 as of May 16.

Helms told a Goldsboro rally over the weekend he is worried about complacency.

''No matter who the other side nominates, if it's Mortimer Snerd, they're going to get 40 or 45 percent of the vote in November, right off the top,'' he said. ''It's going to depend on people in this state who believe in conservative principles to get to the polls.''

Beyle said that while Gantt and Easley are gunning for Helms, they also may be thinking about future bids for office.

''They're keeping their sights on the main target - which is in November - and there is no question they are trying to shape the issues rather than give Helms the chance to shape them,'' Beyle said.

''But I think also there is some feeling that if they don't do well in June or November, they want to do well in 1992.''