  We present a theory of superconductivity in twisted bilayer graphene in which
attraction is generated between electrons on the same honeycomb sublattice when
the system is close to a sublattice polarization instability. The resulting
Cooper pairs are spin-polarized valley-singlets. Because the sublattice
polarizability is mainly contributed by interband fluctuations,
superconductivity occurs over a wide range of filling fraction. It is
suppressed by i) applying a sublattice polarizing field (generated by an
aligned BN substrate) or ii) changing moir\'e band filling to favor valley
polarization. The enhanced intrasublattice attraction close to sublattice
polarization instability is analogous to enhanced like-spin attraction in
liquid $^3$He near the melting curve and the enhanced valley-singlet repulsion
close to valley-polarization instabilities is analogous to enhanced
spin-singlet repulsion in metals that are close to a ferromagnetic instability.
We comment on the relationship between our pseudospin paramagnon model and the
rich phenomenology of superconductivity in twisted bilayer and multilayer
graphene.
