  Xu et al. observed enhanced Nernst effect and Iguchi et al. observed patched
diamagnetism, both well above $T_c$ in underdoped high-$T_c$ superconductors
(HTSCs). A new mechanism is proposed here, which seems to naturally explain, at
least qualitatively, these observations, as well as the d-wave nature and
continuity of pseudogap and pairing gap, the tunneling conductance above $T_c$,
as well as $T^*(x)$, $T_{\nu}(x)$, $T_c(x)$, etc. This mechanism combines
features of dynamic charged stripes, preformed pairs, and spin-bags: At
appropriete doping levels, the doped holes (and perhaps also electrons) will
promote the formation of anti-phase islands in short-range anti-ferromagnetic
order. On the boundary of each such island reside two doped carriers; the
unscreened Coulomb repulsion between them stabilizes its size.
Superconductivity results when such ``pre-formed pairs'' Bose-condense.
