€The white dwarf in CVs is the relic of the more massive
star in
the binary, already past a giant phase
€The secondary star will have spent some time in the
envelope of the primary red giant perhaps accreting material from it
€Dynamical friction reduces the separation of the remnant
core of
the primary and the secondary, causing the secondary to spiral inwards and
perhaps contributing to the ejection of the envelope
€After this phase have a detached hot white dwarf with a
main sequence
secondary; such stars are known (eg BE UMa) and show strong
reflection effects from the hot primary illuminating the secondary
€Further angular momentum losses can shrink the binary separation until the
secondary comes into contact with its Roche lobe, and mass transfer starts, giving
rise to a CV
€Alternatively in longer period systems the secondary can evolve, increasing
in size and filling its Roche lobe