Two senior members of the presidential campaign staff of Massachusetts Gov. Michael S. Dukakis (D) are losing their jobs in a delayed fallout from the videotape affair that cost Dukakis his campaign manager and political director earlier this fall, informed sources said last night.

Press secretary Patricia O'Brien and field director Jack Corrigan are being replaced in the latest shakeup, but both are staying with the campaign in other and reportedly lesser roles, according to reports in Boston and Washington political circles.

Campaign manager Susan Estrich, who instigated the reorganization, is scheduled to announce new titles and positions for O'Brien and Corrigan today. Reached last night, she declined to confirm or deny any of the changes. Corrigan reportedly will be succeeded by Tad Devine, who has been handling delegate slating for Dukakis, and Leslie Dach, the campaign's communications director, will fill in for O'Brien at least on a temporary basis.

The Boston Globe and Boston Herald reported rumors of O'Brien's demotion yesterday morning.

The upheaval comes at an awkward time for the Dukakis campaign and is viewed by insiders as symptomatic of continuing problems following the resignations Oct. 1 of Dukakis' campaign manager and longtime chief political strategist, John Sasso, and Sasso's top deputy, veteran Democratic operative Paul Tully.

The two quit after acknowledging that they had sent videotapes to several news organizations showing that Sen. Joseph R. Biden Jr. (D-Del.), then a Dukakis rival, had borrowed heavily, and, on occasion, without acknowledgment, from a dramatic speech in a campaign commercial used last spring by British Labor Party leader Neil Kinnock. The "plagiarism" controversy eventually led to Biden's withdrawal from the race, but the backlash hit Dukakis, who had relied on assurances from Sasso and Tully to deny that his campaign had any part in the incident.

Only when reporters continued to turn up evidence linking the Dukakis campaign to the tapes did Sasso and Tully resign.

Corrigan was also implicated in the incident, when he acknowledged he had sent the tape to one organization. But Dukakis did not ask him to quit, saying the veteran Boston political organizer had operated at Sasso's instruction and that "mistake does not merit dismissal."

O'Brien joined the Dukakis campaign when it began last spring, after many years as a reporter, most recently in the Knight-Ridder Washington bureau. She apparently had made the transition to press secretary, but when the Boston Globe printed a long post-mortem on the videotape affair, depicting O'Brien as the one person who had early suspicions of wrongdoing and who worked to get the story out in the open, she encountered criticism from others in the campaign. They accused her of prolonging the controversy and protecting her reputation at the cost of others.

Estrich, a 35-year-old Harvard law professor who had been doing issues work for the campaign, took over from Sasso last month, with Paul Jensen, a former Carter administration official with strong labor ties, succeeding Tully as political director. Estrich and Jensen had worked together on the 1984 Mondale campaign.

In the last six weeks, Dukakis, who had surged to the front of the Democratic pack in fund-raising and moved ahead of all the other candidates except Jesse L. Jackson in some national polls, appeared to many observers to have lost both enthusiasm and momentum.