A federal judge in Boston has refused to dismiss charges against 18 aides and organizations of Lyndon H. LaRouche Jr.'s 1984 presidential campaign, rejecting defendants' arguments that they are being prosecuted because of LaRouche's extremist political views.

U.S. District Judge Robert E. Keeton said in a ruling last week that there is no evidence to support defense claims that the 1984 Democratic presidential campaigns of former vice president Walter Mondale, and Sens. Alan Cranston, John Glenn and Gary Hart committed campaign-financing violations comparable to those alleged against the LaRouche supporters.

Attorneys in the case met yesterday to discuss problems with jury selection because of heavy publicity the case has received and its political overtones.

In seeking dismissal of the indictment charging the LaRouche organizations and backers with mail fraud and obstruction of justice, defense attorneys argued that the campaigns of Mondale, Cranston, Glenn and Hart each violated campaign-financing laws but were not subjected to criminal prosecution.

The attorneys contended that the LaRouche backers were indicted because of a government vendetta against the political extremist, who has said he will run for president again in 1988.

"The irregularities in the other campaigns allegedly involve bounced checks, outstanding loans, loan settlements at a low rate, illegal delegate committees and illegal corporate loans," Keeton ruled.

"The charges against these defendants involve soliciting money by false pretenses, unauthorized credit card charges and obstruction of justice . . . . The specific conduct underlying the charges against these defendants is quite different than anything alleged in the irregularities of the other campaigns."

The 13 individuals and five LaRouche organizations are accused of formulating a fraud scheme designed to finance LaRouche's 1984 presidential bid by making more than 2,000 un-authorized credit card charges, totaling more than $1 million.

Some of the defendants also are charged with obstructing the federal investigation of the alleged scheme.

The defendants include the LaRouche Campaign, Independent Democrats for LaRouche, Caucus Distributors Inc., Campaigner Publications Inc. and the National Caucus of Labor Committees.

The government alleges the defendants not only fraudulently obtained money for LaRouche through credit card fraud but also solicited money by telling prospective donors it would be used for AIDS research, and to finance the Strategic Defense Initiative, antidrug campaigns and energy projects.