External candidates for the vacant post of general secretary of the Association of University Teachers could be blocked by the union's executive committee.
The potential bar on outsiders emerged as battle lines began to be drawn over proposals for a merger with rival lecturers' union Natfhe.
The 24-strong AUT executive will decide on the process for the election at a meeting next month. Under the standard procedures for electing general secretaries, the union's rules allow it to open the post to external candidates.
But as outgoing general secretary David Triesman has left prematurely, to take up a job as the Labour Party's general secretary, the executive might implement procedures for a by-election that would exclude external candidates.
The executive is faction free, but views on a suggested merger with Natfhe and the suitability of potential internal candidates could polarise its deliberations about the process. AUT officers have yet to make their formal recommendation as to the election process.
There are few procedural precedents. Incumbents before Mr Triesman took the post in 1992 were appointed without election.
AUT president Natalie Fenton, who this week ruled herself out as a candidate, said the union must open the election to as wide a field as possible in accordance with equal opportunities best practice.
One executive member said it would be astounding if the competition was closed to outsiders, not least because there was a dearth of talent inside the AUT.
The bar could rule out an election campaign based on a merger.
One prominent potential candidate for the general secretary's job is Tom Wilson, head of Natfhe's universities department, who supports a merger.
Mr Wilson, a former AUT assistant general secretary, has yet to comment on whether he wants to stand, but he has stressed that the election raises fresh hopes of a merger. He has made himself unpopular among some AUT members for what they perceived as attacks on old universities' privileges during his time at Natfhe.
At least two key executive members openly oppose a merger: Philip Burgess, a psychologist at Dundee University, and Peter Borcherds, of Birmingham University, who is stepping down from the executive next month. Dr Borcherds opposed Mr Triesman's move for a "confederation" with Natfhe at his election in 1992.
Others are known to be pro-merger. Birmingham's Gargi Bhattacharyya said that a merger would be better for members and the sector.
Two other executive members confirmed they supported merger plans but asked not to be named.
So far, no one has declared an intention to run. Outgoing AUT president Alan Carr and executive member Penny Holloway have been mooted as potential candidates. Neither was available for comment as The THES went to press.
Whether the election is restricted to internal candidates or open, the AUT is likely to be without an official leader until early next year. The election process will start in early October and elections are expected in late November or early December.
Assistant general secretary Paul Cottrell, who is expected to be a candidate, will stand in as acting general secretary.