Atlanta — The Ku Klux Klan is running into trouble.
After three years of steady gains, Klan membership appears to have plateaued and may even be declining, according to informed Klan-watchers.
Increased legal attacks against the KKK and feuding among Klan factions are cited as causes of the its troubles.
At the same time there is increased community resistance to the Klan, which may be sending a signal to Klan factions that their cross burnings, violence, and racist literature are not welcome.
Anti-Klan marches in Connecticut, Georgia, and several other states have been drawing much larger crowds than Klan rallies. Many schools across the country are ordering materials for teaching about the violence and bigotry of the Klan.
Earlier this year, when a black family in Marietta, Ga., and another in the Pittsburgh suburb of Brentwood had crosses burned on their yards, a hallmark of the KKK, white neighbors rallied to support the victims.
After the Marietta incident, community leaders held interracial breakfasts with law enforcement officials, church leaders, and others to let it be known that ''we do not condone this,'' says Hugh Grogan, a former member of the Marietta City Council.
Opposition to Klan activities ranges from state task forces to editorials and letters to editors. The National Anti-Klan Network, a coalition of several dozen groups, is training community leaders to conduct peaceful counter-rallies pressing for prompt police investigation of Klan incidents, and educating teachers and the public about the Klan.
Georgia has become one of the main staging areas for Klan activities and appears to be the one state where the Klan is gaining members, says Irwin Suall, of the Jewish Anti-Defamation League. For years the ADL has monitored Klan activities.
But the gains in Georgia are being more than offset by losses in other states , including Alabama, Mississippi, North Carolina, and Tennessee, Mr. Suall says.
Klan membership appears to have leveled off, according to Suall and Randall Williams, director of the Klanwatch project of the Southern Poverty Law Center in Montgomery, Ala. Membership may even have ''declined slightly,'' Mr. Williams says.
The ADL estimates Klan membership was 6,000 to 8,000 in 1978. Over the next three years it nearly doubled, to just under 12,000, according to Mr. Suall.
This ''moderate resurgence'' must be seen in perspective, he says; in the mid-1960s, for instance, membership reached about 55,000. (In the 1920s, he adds , it reached 3 to 5 million.)
But the Klan is far from extinct. A Klanwatch study shows there has been Klan activity in 21 states in the past few months.
And commmunity resistance has often been the least in areas of greatest Klan activity -- mostly in the deep South, says Mike Vahala, a Klanwatch staffer member.
A jury selection survey used in a trial of Klansmen accused of the 1980 shooting of five elderly black women in Chattanooga, Tenn., showed that two-thirds of the white respondents were opposed to the Klan; but one-third of them were not.
The Klan is only a reflection of other forms of racism that persist in society, according to Rev. C. T. Vivian of Atlanta. The Rev. Mr. Vivian was an aide to the late Rev. Dr. Martin Luther King Jr. and is now chairman of the National Anti-Klan Network.
'' White America is ashamed of the Klan,'' he adds. But that is not enough, he insists -- people must actively oppose it.
Increasingly, it appears, more people are doing just that -- in various ways:
* In Texas, where a faction of the KKK has operated several paramilitary camps, a US district court judge has just outlawed them. The Southern Poverty Law Center (SPLC) in Montgomery, Ala., which brought the suit, has filed a similar one to ban similar camps in Alabama.
* When some 35 robed Klansmen marched in Meriden, Conn., in March, more than 800 people marched the same day in Hartford, Conn., in protest against the Klan.
* A 70-page SPLC report designed for students, ''The Ku Klux Klan: A History of Racism and Violence,'' has sold out (mostly to school officials) its first printing of 50,000 copies. 100,000 more are being printed.