Arlington prosecutor Henry E. Hudson said this week that he expects to take office as the U.S. attorney for the Eastern District of Virginia by the last week of this month or the first week in June, a schedule that is expected to intensify the campaigns of two Democrats who hope to succeed him.

Hudson, a Republican who was unanimously confirmed by the Senate for the federal post Tuesday night, said he intends to meet with Arlington's four Circuit Court judges next week to discuss his departure. This week, he is completing a report by a national pornography commission he heads.

"I want to make the decision on a starting date compatible with their timetable for picking a successor," Hudson said of the judges, who will appoint an interim commonwealth's attorney to serve until the Nov. 4 election. The winner of the election will serve the year remaining in Hudson's four-year term.

Two candidates are seeking the Democratic nomination to succeed Hudson: Helen Fahey, Hudson's chief deputy and a 10-year employe of the office, and Brendan Feeley, an assistant prosecutor for three years in the mid-1970s who has a private criminal law practice. In anticipation of Hudson's departure, county Democrats have split into two camps and begun campaigning for Fahey and Feeley. No date has been set for the vote.

Local Republican leaders have said they did not expect to field a candidate, a move that virtually guarantees that the person nominated by the Democrats this spring will be Hudson's successor. No independents are expected to run.

The judges, themselves selected by a Democratic-controlled Virginia legislature, are expected to appoint an interim prosecutor within days of Hudson's departure and that person is expected to be a Democrat. Fahey is heavily favored in local legal circles to win the appointment because of her experience.

But Feeley, who said he would not seek the appointment, is backed by several party regulars who are experienced in getting out the vote and who say he should win the nomination because of his experience in the office and willingness to run against the popular Hudson in 1983.

Hudson, who has been county prosecutor for six years, said he does "not intend to make a formal endorsement, but I would not preclude private communication with the Circuit Court judges."

He said he would like to return to Arlington to prosecute some cases he has worked on for months, such as a murder case involving an alleged exorcism, if his successor approves and his new job allows.