I tracked down how he gets to 3 million or rather 2.8 million. This is the relevant extract from the Richman study:
Quote:
Taking the least conservative measure e at
least one indicator showed that the respondent voted e
yields an estimate that between 7.9% and 14.7% percent
of non-citizens voted in 2008. Since the adult noncitizen
population of the United States was roughly
19.4 million (CPS, 2011), the number of non-citizen
voters (including both uncertainty based on normally
distributed sampling error, and the various combinations
of verified and reported voting) could range from just
over 38,000 at the very minimum to nearly 2.8 million at
the maximum.
|
Quote:
The adjusted estimate of 6.4 percent for 2008 is quite substantial,
and would be associated with 1.2 million noncitizen
votes cast in 2008 if the weighted CCES sample is
fully representative of the non-citizen population
|
pp. 152-153.
http://www.judicialwatch.org/wp-cont...hman-et-al.pdf
Now the study is far from definitive, as someone who often works with statistics, their method where you take a small sample size and extrapolate to a much larger group can easily lead to a gross over- or under- representation.
The only thing the study really shows is that there probably is an issue, but no one knows how big it is.