The "political leaders" of both parties do not want to do anything to stop those thaat cross the border illegally in order to avail themselves of the American welfare system which includes having baby after baby on the system. crossings.
The reason is that the Republicans hope that the babies that are born over here will vote for the Republicans upon reaching voting age and the Democrats hope that they will vote for the Democrats.
Both parties are deceiving themselvel with this line of thinking.
When they get enough of like voters, they will elect their own kind and the members of their own parties.
Neither party cares which way they vote. Our election process devolved into cheap theater decades ago. The elites in both parties want to bring the illegals in to maintain privilege. They see this as a way to break the conservative movement which is based on merit and principle rather than privilege.