I've looked at the wiki and it seems like the only republican group to have endorsed Marc Lamb are Latinos for Trump. Also while he's still far from Lake, it's not as bad as I thought honestly, she seems to lead him by 2-1 with still two months to go and he appears to be the one gaining in polling. Given the terrrible general election polling of Lake against Gallego, republicans would be wiser to nominate him. I think Trump probably wishes he hadn't endorsed Lake as even he can tell how much of a drag she appears to be, but given how absolutely loyal to him she has been, he doesn't want to betray her.
The problem is Republicans in the Trump era are astonishingly stupid when it comes to who to nominate.