Missingness is a second intervention node. Writing Delta = 1
for an observed outcome, the joint intervention is "set A = a
and Delta = 1", so the clever covariate carries both
probabilities,
H = Delta/pi(A, X) * [A/g(X) - (1 - A)/(1 - g(X))], with
pi(a, X) evaluated at the counterfactual arm. The initial
outcome regression is fitted on complete cases only, and the
fluctuation Q*(a, X) = Q(a, X) + eps/(g_a(X) pi(a, X)) uses the
arm-specific denominator. With no missingness pi == 1 and the
estimator collapses onto the standard point-treatment TMLE.
