Under the Bush administration, the Department of Homeland Security engaged in a small number of showy but not overly effective immigration raids. Under the Obama administration, the DHS switched to (in addition generally not doing its job) what are called "silent raids" where they audit a company's employment records and then request that the employees are fired if they can't prove they're here legally. That lets illegal aliens stay in the U.S. and simply go find work at another company. And, that helps the Democrats maintain a power base. (Over nine months ago I urged people to ask Janet Napolitano about this at one of her public appearances).

Not only does the Obama administration cause long-term difficulties for American workers with this policy, but they're also letting employers off the hook (link):

...ICE audit records obtained recently through a Freedom of Information Act request show that the agency has, in many instances, failed to punish companies found to have significant numbers or high percentages of workers with questionable documents... The records show inspectors identified more than 110 companies with suspect documents, with nearly half of those having questionable paperwork for 10 or more workers... In total, the agency ordered 14 companies to pay fines of nearly $150,000, but noted no employer arrests in connection with any of the cases...

ICE doesn't have much of a defense:

[ICE points] to the fact that this fiscal year the agency has ordered businesses to pay a record-setting $4.6 million in civil penalties and has arrested more than 150 employers, managers or supervisors. However, some of the arrests stem from investigations going back several years. And the fines reflect enforcement actions that date as far back as 2007, including $360,000 from the 2008 raid of a Houston rag factory and more than $536,000 from a 2007 Ohio chicken factory raid. ...ICE did not have a breakdown of how much of the $4.6 million or how many of the arrests stemmed directly from the audit initiative, which began in July 2009.

Note also that one of the components of comprehensive immigration reform is increased enforcement, including cracking down on employers of illegal aliens. Some Democrats even stress that they want to do that now. Are you willing to trust that "reform" would include stepped-up enforcement given the above?

Sidenote: the article also quotes Angela Kelley of the Center for American Progress:

"You have this drip, drip, drip of I-9 enforcement audits all over the country, and it has the same effect - people don’t come to work the next day."

Those she's referring to aren't supposed to be here in the first place; she's on their side and not on the side of American workers.