A relatively new talking point from supporters of comprehensive immigration reform is that their amnesty would help American workers by preventing illegal aliens from lowering wages. This is fallacious for at least two reasons:
1. Not all jobs are open to illegal aliens; only some industries and companies are lax about checking whether someone is eligible for a job. Legalization would mean that current illegal aliens would be able to get any job for which they're qualified. That would increase the competition for a large number of job categories, leading to lowered wages in those job categories. For instance, an illegal alien nurse can't probably work as a nurse illegally. Yet, if they're legalized, they can then go to work as a nurse (licensing issues aside). That would lower wages for U.S. citizen nurses.
2. There will always be a demand from corrupt companies for illegal workers. Those far-left, racial power, and other groups that currently oppose enforcement of our immigration laws will continue opposing enforcement even if they get their "reform". Those groups will enable post-"reform" illegal immigration. That will leave us with a fresh supply of millions of new legal workers and a growing population of new illegal aliens.