  A significant fraction of RR Lyrae stars exhibits amplitude and/or phase
modulation known as the the Blazhko effect. The oscillation spectra suggest
that, at least in most of the cases, excitation of nonradial modes in addition
to the dominant radial modes is responsible for the effect. Though model
calculations predict that nonradial modes may be excited, there are problems
with explaining their observed properties in terms of finite amplitude
development of the linear instability. We propose a scenario, which like some
previous, postulates energy transfer from radial to nonradial modes, but avoids
those problems. The scenario predicts lower amplitudes in Blazhko stars. We
check this prediction with a new analysis of the Galactic bulge RR Lyrae stars
from OGLE-II database. The effect is seen, but the amplitude reduction is
smaller than predicted.
