"Sheriff Ansell Keeps His Promise" said the headline in "The Blue Ribbon Democrat," the 1974 campaign newspaper of the Prince George's County Democrats. Sheriff Don E. Ansell, the paper said, had kept his promise to bring a "high degree of professionalism" to his department.

Directly under the Ansell endorsement, the party organ cited State's Attorney Arthur A. Marshall as an "outstanding prosecutor."

Two weeks ago, the "outstanding prosecutor" announced the indictment by a county grand jury of the highly touted sheriff for misappropriation, perjury and filing a fraudulent state income tax return. The indictment seemed to provide the demoralized Republicans in the county with a ready-made campaign issue. Or did it?

"Any public figure whose publicity is not good doesn't help his party," said Marshall last week about the indictment of his 1974 running mate. Ansell's assistant sheriff and two deputy sheriffs were also indicted.

"I think the Republicans will make as much of it as they can," predicted Lance Billingsley, chairman of the Prince George's Democratic Central Committee.

How much they can make of it may depend on how effectively they are able to tie Ansell in the public mind with the Democratic Party organization. Republicans were quick to seize on the indictments as no more than could be expected in any county so completely dominated by one party (the Democrats hold all elected positions).

Most Democrats, meanwhile, were wishing the whole thing would go away or, in any case, strongly suggesting that Ansell's guilt or innocence and the administration of his department - sharply criticized in a separate grand jury report - had nothing to do with them.

Following the precedent of Gov. Marvin Mandel, the sheriff made it known that he plans to remain in office unless and until he is convicted and sentenced. Party chairman Billingsley suggested the day of the indictment that Ansell might have to step aside, keeping the title but not the responsibility, pending his trial. Other Democrats did not immediately second the idea. Through an aide, County Executive Winfield M. Kelly said that remaining in office was a "personal decision" only the sheriff should make.

The initial reaction of Kelly political intimate John Lally was that the indictment would affect only the indicted.

After two weeks, Billingsley, also, was having second thoughts about the indictment's impact. At first, he said, "I thought people here would say Prince George's is just like Baltimore County and the state . . . Since then, it seems the impact is not as great as I'd thought."

Marylanders have become used to the indictment of so many public officials in recent years, Billingsley suggested, that "the shock value is not high." Further, he said, prosecution of Ansell by fellow Democrat Marshall would serve to mute the overall impact on the party's image.

On Republican, meanwhile, suggested that the indictments were timed by Marshall to boost his own image, at Ansell's expense, on the eve of the 1978 elections.

The investigation by Marshall's office and the grand jury resulted, according to Marshall, from an article in The Washington Post March 28 contrasting Ansell's affluent lifestyle with his modest sheriff's income of $25,500 a year.

Ansell, the 40-year old sheriff elected seven years ago on a reform platform, is a former state trooper and private investigator who had impressed Peter F. O'Malley, he reputed unofficial Democratic kingmaker, as a serious law enforcement official.

"Don was a Maryland state trooper who convicted a client of mine by use of the lie detector," O'Malley recalled this past spring. Later, Ansell sought O'Malley's support for sheriff and, by O'Malley's account, received at least his encouragement.

Marshall, seeking re-election that year, ran on a slate in the Democratic primary opposed to the O'Malley-backed faction that included Ansell John R. Miles, an attorney closely associated with O'Malley, opposed Marshall. Ansell assisted by holding a fun draiser at his home for Miles, who lost.

O'Malley recalls that he and Marshall were "bitter, bitter adversaries" for many years. "It was probably one of th few personal antogonisms that occurred in my political involvement," O'Malley said. "I did everything possible to see him removed from office and failed. And he did everything possible to gain a strong handle on me. Whatever has occurred we are now comfortable with each other. He does a very good job in his shop."

Marshall, whose reputation as a maverick in Prince George's politics seemed to evaporate in the unity surrounding the 1974 "Blue Ribbon" slate, sounded more his own man last week. Of O'Malley, Marshall said, "I found I can do my jon with or without him."

Throughout the Ansell indictments, there remained much skepticism around the Upper Marlboro court-house that any criminal charges would result. That they have is likely to be a double-edged sword in Prince George's politics with no sure winners.