  Recent experiment has unveiled an anomalously strong electron-electron
attraction in one-dimensional copper-oxide chain
Ba$_{2-x}$Sr$_x$CuO$_{3+\delta}$. While the near-neighbor electron attraction
$V$ in the one-dimensional extended Hubbard chain has been examined recently,
its effect in the Hubbard model beyond the one-dimensional chain remains
unclear. We report a density-matrix renormalization group study of the extended
Hubbard model on long four-leg cylinders on the square lattice. We find that
the near-neighbor electron attraction $V$ can notably enhance the long-distance
superconducting correlations while simultaneously suppressing the
charge-density-wave correlations. Specifically, for a modestly strong electron
attraction, the superconducting correlations become dominant over the CDW
correlations with a Luttinger exponent $K_{sc}\sim 1$ and strong divergent
superconducting susceptibility. Our results provide a promising way to realize
long-range superconductivity in the doped Hubbard model in two dimensions. The
relevance of our numerical results to cuprate materials is also discussed.
