We study the long-time stability of soliton solutions to the
Korteweg-deVries equation. We consider solutions $u$ to the KdV with
initial data in $H^s$, $0 \leq s < 1$, that are initially close in
$H^s$ norm to a soliton. We prove that the possible orbital
instability of these ground states is at most polynomial in time.
This is an analogue to the $H^s$ orbital instability results of
[7] for the nonlinear Schrödinger equation, and obtains
the same maximal growth rate in $t$. Our argument is based on the
"I-method" used in [7] and other papers of
Colliander, Keel, Staffilani, Takaoka and Tao.