Republican supporters of presidential hopeful Rep. John B. Anderson (R-Ill.) said yesterday they will continue to campaign on his behalf for the May 6 D.C. primary, despite Anderson's decision to run as an independent.

District of Columbia Anderson coordinator Howard Gillette said the local campaign committee is asking supporters to vote for Anderson in the preferential portion of the primary balloting though the group will withdraw its slate of delegates for the Republican National Convention.

Anderson's major competition in the preferential race is expected to come from candidate George Bush. Front-runner Ronald Reagan will not compete in the so-called "beauty contest," though one of two uncommitted slates of D.C. convention delegates is leaning toward Reagan.

Gillette said the primary campaign would be continued in order to "send the front-runner a message" from District of Columbia voters.

A major focus of the Anderson campaign has been to attract support from Democrats and independents through an intensive effort to get these voters to re-register as Republicans.

According to the D.C. Board of Elections and Ethics, more than 2,500 new GOP voters were registered in recent months. Gillette said he believed "more than 90 percent" of this surge can be attributed to the efforts of the Anderson forces, who distributed nearly 5,000 voter registration cards.

Anderson has demonstrated his ability to appeal to college students nationwide, and on April 2 drew an enthusiastic, overflow crowd at George Washington University here.

Gillette estimated that "no more than 300 or 400" of the new registered Republicans were drawn from the city's college campuses. The bulk of the new GOP voters are "young people in their 20s who are working and a lot of whom haven't voted before," he said.

Anderson forces will spend no money on the District of Columbia campaign, relying instead on volunteers, Gillette said. He said no more local appearances by the candidate are scheduled.

He said the local campaign is in a state of flux because of Anderson's decision to forego his run for the GOP nomination and make the attempt as an independent.

"We've caucused, but we haven't really decided anything," Gillette said. "As long as Anderson stays in, I think most of the group will stay with him."

Most of the Anderson workers have come from Ward 3, the largely white and affluent portion of the city west of Rock Creek Park, Gillette said. Support has also come from the Capitol Hill area and from Adams Morgan, he said.