Another Rule Trump Could Break: Primary Challengers Doom Incumbent Presidents

An incumbent president with a middling approval rating and mounting controversies is usually an easy draw for primary challengers.

Look to Gerald Ford, Jimmy Carter and George H.W. Bush. All three presidents survived intraparty battles, but those primary fights left their reelection campaigns so hobbled — exposing longstanding weaknesses with their bases — that each went on to lose out on four more years in the White House.

But even if a viable GOP challenger to President Trump does emerge, it's unlikely he or she could make much headway or have a lasting impact on the president's chances in November. That's because Trump's firm grasp on the Republican Party could help him emerge not only victorious, but relatively unscathed by a primary challenge.

Political polarization is higher than ever, according