Republicans allowed Democrats to import millions of voters to overwhelm native voters
600 voters with Hillary having more than a 20 point lead with indy voters is definitely a biased propaganda hit piece that Politico is famous for. Trump has plenty of shortcomings and hurdles ahead but his strength with indy voters has been well substantiated with huge chunks of crossovers.
They didn't just allow it, they participated, joined, encouraged, advocated, etc. just as much as the DEMs did. See GWB "Comprehensive immigration bill" for example, and half-baked immigration enforcement going back decades.