Because the Democrats have absolutely nothing to point at and brag about when it comes to what the Biden presidency has brought Americans, their shouts of "threat to democracy" about Trump combined with lies about Project 2025 being the official Republican platform are all they have left. 

One Democrat, a New Hampshire State Rep., took things to the next even more nutty level with this claim: 

Yes, we're sure Vance would support something that would get his own wife deported (cue massive eye roll). There's a whole lotta BS in that tweet.

The claim got nuked by Community Notes and it couldn't have been more deserved: 

Here's what the note says in case it's not visible above:

Usha Vance is an American citizen who was born in California. There are no proposals contained in the Heritage Foundation’s “Project 2025” that advocate for the deportation of American citizens.

But since when do these Democrats care about facts? 

As usual the Democrats would like everybody to conflate legal immigration with illegal immigration.

As usual, if you want to know what these lefties are up to just watch what they accuse others of.