We use the theta lift to study the multiplicity with which certain automorphic representations of cohomological type occur in a family of congruence covers of an arithmetic manifold. When the family of covers is a so-called 'p-adic congruence tower' we obtain sharp asymptotics for the number of representations which occur as lifts. When combined with theorems on the surjectivity of the theta lift due to Howe and Li, and Bergeron, Millson and Moeglin, this allows us to verify certain cases of a conjecture of Sarnak and Xue.The second author is supported by NSF grant this ensures that the metaplectic cover of Sp(W ) splits on restriction to G × G ′ by a result of Kudla [6]. Let L ⊂ V be an O E lattice, whose completion in V v we shall assume to be self dual whenever V is unramified, and Γ ⊂ G(R) the arithmetic group stabilising L. Let r be the dimension of the maximal isotropic subspace of V , and define
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