  Recent experiments have demonstrated that the rotational-alignment for the
$N=Z$ nuclei in the mass-80 region is considerably delayed as compared to the
neighboring $N \ne Z$ nuclei. We investigate whether this observation can be
understood by a known component of nuclear residual interactions. It is shown
that the quadrupole-pairing interaction, which explains many of the delays
known in rare-earth nuclei, does not produce the substantial delay observed for
these $N=Z$ nuclei. However, the residual neutron-proton interaction which is
conjectured to be relevant for $N=Z$ nuclei is shown to be quite important in
explaining the new experimental data.
