From this:

Nearly 1.8 million undocumented immigrants could have their deportations suspended for two years, and legally obtain jobs here, under President Obama’s recent policy to give them leniency.

That number is significantly higher than the earlier estimates of a maximum of 1.3 million immigrants who could benefit, thanks to newly released set of guidelines that expanded the pool of eligible applicants, said the Migration Policy Institute...

The new MPI report said the revised estimate reflects "the updated (Department of Homeland Security) guidelines that youth lacking a high school or GED degree would be eligible to apply for deferred action as long as they have re-enrolled by the date of their application."

See DREAM Act for extensive coverage of that bill and of Obama's new policy. See Obama immigration for extensive coverage of his actions on the wider topic.

In July 2012, the number of people in the civilian work force aged 25 or more and with less than a high school diploma was around 11.4 million, and the number with a high school diploma but no college was around 37 million (bls.gov/web/empsit/cpseea05.htm).

Those workers are the ones who are going to be most negatively impacted by Obama's policy, as they see hundreds of thousands of new legal workers able to compete with them for lower-skilled jobs. Needless to say, most of the workers harmed by Obama's amnesty will be Democrats.