  The nature of the normal state of cuprate superconductors continues to
stimulate considerable speculation. Of particular interest has been the linear
temperature dependence of the in-plane resistivity in the low-temperature
limit, which violates the prediction for a Fermi liquid. We present
measurements of anisotropic resistivity in La$_{2-x}$Sr$_x$CuO$_4$ that confirm
the strange-metal behavior for crystals with doped-hole concentration $p=x >
p^\ast \sim 0.19$ and contrast with the non-metallic behavior for $p<p^\ast$.
We propose that the changes at $p^\ast$ are associated with a first-order
transition from doped Mott insulator to conventional metal; the transition
appears as a crossover due to intrinsic dopant disorder. We consider results
from the literature that support this picture; in particular, we present a
simulation of the impact of the disorder on the first-order transition and the
doping dependence of stripe correlations. Below $p^\ast$, the strong electronic
interactions result in charge and spin stripe correlations that percolate
across the CuO$_2$ planes; above $p^\ast$, residual stripe correlations are
restricted to isolated puddles. We suggest that the $T$-linear resistivity
results from scattering of quasiparticles from antiferromagnetic spin
fluctuations within the correlated puddles. This is a modest effect compared to
the case at $p<p^\ast$, where there data suggest that there are no coherent
quasiparticles in the normal state.
