John Patten, a Clackmannan primary headteacher, led the move and appealed to delegates not to be "elitist and Luddite". Instructors, librarians and researchers were eligible for membership. This gave the invitation to nursery nurses "a compelling logic" and would extend the union's influence in an expanding pre-fives sector, Mr Patten said.
Gillian Kulwicki, a Glasgow nursery head, said she could not deliver quality provision without nursery nurses and their jobs were "inextricably linked".
But the demarcation lines were quickly drawn by Drew Morrice, North Lanarkshire secretary, who cautioned that teachers' status could be undermined.
Several speakers warned of poaching members from other public sector unions to which Scotland's 2,300 nursery nurses belong.
Mr Patten also challenged as "ridiculous" a claim by Norma Watson, a nursery head and past union president, that some teachers would desert the EIS if membership was widened to include nursery nurses. Nursery classrooms would continue to be led by nursery teachers, he stressed.
The defeat for nursery nurse membership came despite heavyweight support from Moira McCrossan, the new vice-president, and Margaret Nicol, convener of the union's equal opportunities committee, who reminded delegates that they were part of an educational union not a teachers' union.
But delegates were swayed by a prophecy from Pat Swanson, Renfrewshire: "There will come a day when the interests of nursery teachers will be different from those of nursery nurses."