  Most of the useful information about inflationary gravitational waves and
reionization is on large angular scales where Galactic foreground contamination
is the worst, so a key challenge is to model, quantify and remove polarized
foregrounds. We use the Leiden radio surveys to quantify the polarized
synchrotron radiation at large angular scales, which is likely to be the most
challenging polarized contaminant for the WMAP satellite. We find that the
synchrotron E- and B-contributions are equal to within 10% from 408-820MHz with
a hint of E-domination at higher frequencies. We quantify Faraday Rotation &
Depolarization effects and show that they cause the synchrotron polarization
percentage to drop both towards lower frequencies and towards lower multipoles.
