Republicans already ran a campaign blasting Democrats as socialists. It didn't work.

“Their attacks backfired,” said Democratic state Rep. Jennifer O’Mara, a first-time candidate who won a GOP-held seat in the Philadelphia suburbs. “They protested an event I was at and handed out fake $10,000 bills that said ‘In Socialism We Trust’ with my face on it. They went really low, and it didn’t work.”

The election in Pennsylvania serves as a case study of a campaign strategy that could prove critical to Trump’s reelection — or undoing — in 2020. The president and his allies have made it no secret they plan to brand the eventual nominee — no matter who it is — as a socialist on the fringe of the political spectrum. If centrist voters are uncomfortable with Trump, think about the radical experiment the other side is offering, the theory goes.

But Democrats say the tactic failed in Pennsylvania partly because it didn’t ring true: Many of the party’s candidates ran as moderates, they said, and even most progressives who campaigned for office were far from socialists. Plus, they argue, the GOP has cried wolf for years when it comes to socialism, including by labeling the Affordable Care Act as far left.