Two past Republican allies of Prince George's County Executive Lawrence Hogan, including one who was considered to be his political protege, are expected to break ranks with Hogan today by endorsing Bowie Mayor Audrey Scott, instead of Hogan's son, in the April 7 Republican primary for Congress.

The expected endorsements by John B. Burcham Jr., who ran in 1974 and 1976 for Congress as the Hogan-endorsed candidate, and Kevin Igoe, last year's Republican candidate for the 5th Congressional District, came as a surprise to Lawrence Hogan Jr.'s campaign staff. The younger Hogan had asked both men to support him and Burcham was offered the largely titular job of campaign chairman.

However, according to several Republican friends of Burcham and Igoe the endorsement had been in the works for at least a few weeks, ever since the senior Hogan tried to clear the Republican primary field for his son by pressuring Scott and Burcham, then a possible candidate himself, to stay out of the race.

Both Burcham and Igoe were angered by the attempts, according to Republican friends, and they agreed to endorse Scott once approached by her campaign staff, despite initial worries by the two that Hogan, the county's dominant Republican, would attempt to harm them politically in the future. Hogan has denied that he applied pressure tactics to clear the primary field for his son.

Burcham yesterday said only that he would be endorsing Scott because "I think she's a very attractive candidate. She's experienced and she has the potential to attract Democrats and independents in the general [which will be held May 19]." Burcham declined to comment specifically on what effect the older Hogan's involvement had on his decision to endorse Scott except to say, "I'm not doing it for spite or anything of that sort."

The endorsements are considered a coup for Scott, the underdog in what has become a two-person race, and indicate the extent to which this election to fill Gladys Spellman's seat has begun to dredge up old animosities in the county's tiny Republican Party and among state Republican leaders.

There are many county and state Republicans, all but a few of whom request anonymity because of Hogan's perceived political clout and temper, who complain that Hogan Jr. is too young -- he is 24 -- and inexperienced to run for Congress. They have also charged that Hogan had pushed his son into running for the seat simply to test the political waters for his own expected race for the U.S. Senate in 1982.

A few weeks ago, Scott discovered that several influential Republicans, including former U.S. senator J. Glenn Beall, were eager to offer campaign advice and help. And next week, six of the seven Republican state senators are expected to hold a press conference in Annapolis to announce their support for Scott.

Chuck Kline, the press aide for Lawrence Hogan Jr., said yesterday that he did not expect the endorsement of Scott by Burcham and Igoe to carry much weight in the primary campaign. Hogan Jr. has been endorsed by former Republican County executive William Gullett, who was appointed two years ago by Hogan Sr. to run a major department in the county government. Gullett was recently appointed the Hogan campaign chairman.

Kline also said that Rep. Jack Kemp (R-N.Y.) has agreed to host a fund-raiser for Hogan Jr. -- on April 14, a week after the primary. The money is being raising now to help Hogan Jr. fund his primary campaign, but besides, Kline said, "we don't expect [to lose the primary] and apparently neither does Kemp."