Could credible primary rival hurt Trump? History suggests so

WASHINGTON (AP) — “Never Trump” Republicans are anxious to see the president face a credible primary adversary.
But the party may erect political hurdles that could make challenges that are already the longest of longshots even more difficult.
It’s a tough road for a reason: Every incumbent president for four-plus decades who has faced a serious such challenge was weakened enough to ultimately lose reelection.
That encompasses Presidents Gerald Ford, Jimmy Carter and Geor