Dems basically fight any attempts at across the board immigration controls which cater to the large wing of the party that sees any disucssion of controlling immigrants as racism and xenophobia. gop want to build a wall so dems can say the gop is racist against immigrants and get their side riled up to vote against people who hate immigrants.
Dems used to talk tough on immigration but realized it kills their voting with latinos so they backed off. you will never hear a dem platform described as trying to stop the flow of people across the border illegally or handle the large numbers because attempts to do so hurt their election chances....
once the election is over they can move on to something else.