  A unified description of spacelike and timelike hadron form factors within a
light-front model was successfully applied to the pion. The model is extended
to the nucleon to study the role of $q \bar q$ pair production and of
nonvalence components in the nucleon form factors. Preliminary results in the
spacelike range $0 \le Q^2 \le 10 ~ (GeV/c)^2$ are presented.
