  The combined study of the flaring of Active Galactic Nuclei (AGN) at radio
wavelengths and pc-scale jet kinematics with Very Long Baseline Interferometry
(VLBI) has led to the view that i) the observed flares are associated with
ejections of synchrotron blobs from the core, and ii) most of the flaring would
follow a one-to-one correlation with the component ejection. Recent results
have provided mounting evidence that the quasi-regular component injections
into the relativistic jet may not be the only cause of the flux variability. We
propose that AGN flux variability and jet morphology changes can both be of
deterministic nature, i.e. having a geometric/kinetic origin linked to the
time-variable Doppler beaming of the jet emission as its direction changes due
to precession (and nutation). The physics of the underlying jet leads to
shocks, instabilities, or to ejections of plasmoids. The appearance
(morphology, flux, etc.) of the jet can, however, be strongly affected and
modulated by precession. We demonstrate this modulating power of precession for
OJ 287. For the first time, we show that the spectral state of the Spectral
Energy Distribution (SED) can be directly related to the jet's precession
phase. We model the SED evolution and reproduce the precession parameters.
Further, we apply our precession model to eleven prominent AGN. We show that
for OJ 287 precession seems to dominate the long-term variability ($\gtrsim
1\,{\rm yr}$) of the AGN flux, SED spectral state, and jet morphology, while
stochastic processes affect the variability on short timescales ($\lesssim
0.2\,{\rm yr}$).
