Stop Immigrant Undermining of Unions
The Democrats' support of illegal immigration undermines the goals of  unions as it floods the market with extra workers. These additional and illegal workers pose at least  three distinct problems.
First of all, illegal immigration hurts the bargaining power of unions and obstructs their basic purpose, which is to allow workers a way to demand a  higher, more livable wage. Let's say they are trying to negotiate their wages from $8/hr to $12/hr. That increase alone is a tough sell to the owners, but when they compare it to paying illegal immigrants who might work for $4/hr, the increase becomes much more difficult to achieve.
Not only does illegal immigration hurt the bargaining power of unions, but it also impedes their growth. In order for a union to thrive, it spreads from business to business in the same area and industry. Suppose there is a factory that has recently become unionized. Workers from a similar factory in the area will see the prosperity of the unionized workers and  might make plans to become unionized themselves--unless that factory is full of illegal aliens who do not want to be documented any more than they already are.
Additionally, illegal immigration undercuts wage competition of all nearby citizen workers including those in unions. Not only will our example illegal-filled factory not become unionized, but it's unfairly low wages will put the unionized factories out of business or force them to replace union workers with illegals.
The Democratic Party claims to be on the side of unions, but clearly they are not. Their endorsement of out-of-control illegal immigration hurts the expansion of unions and the wages of their workers.