The Post has an oped by Edward Schumacher touting the benefits that undocumented workers have provided for the Social Security system. Many pay taxes without ever collecting benefits.
While his numbers don't seem quite right (he claims that annual payouts would exceed tax revenue over the years 2011-2015 without the $12 billion estimated net contribution from undocumented workers, the trustees report shows taxes exceeded benefits by more than $15 billion in the years 2012-2014), the more important problem is with his logic.
Presumably the point of immigration reform measures would be to normalize the employment situation of immigrants so that the workers who are here are on the books, both paying required taxes and receiving the benefits to which they are entitled, like Social Security. If immigrants get the benefits to which they are entitled, then it will make the finances of Social Security somewhat worse.
In reality this is a trivial issue for the program, which is fully solvent for the next 29 years according to the Congressional Budget Office. An increase in the payroll tax of 0.16 percentage points would fully offset the cost of the payment of benefits to undocumented workers. However, it seems bizarre to advocate that immigrants be brought into the country to pay taxes to a program from which they get no benefit, as Mr. Schumacher seems to be doing.