  Propagation of a viscous fluid beneath an elastic sheet is controlled by
local dynamics at the peeling front, in close analogy with the capillary-driven
spreading of drops over a precursor film. Here we identify propagation laws for
a generic elastic peeling problem in the distinct limits of peeling by bending
and peeling by pulling, and apply our results to the radial spread of a fluid
blister over a thin pre-wetting film. For the case of small deformations
relative to the sheet thickness, peeling is driven by bending, leading to
radial growth as $t^{7/22}$. Experimental results reproduce both the spreading
behaviour and the bending wave at the front. For large deformations relative to
the sheet thickness, stretching of the blister cap and the consequent tension
can drive peeling either by bending or by pulling at the front, both leading to
radial growth as $t^{3/8}$. In this regime, detailed predictions give excellent
agreement and explanation of previous experimental measurements of spread in
the pulling regime in an elastic Hele-Shaw cell \cite{puzovic-2012}.
