A former Trump ally now says the president's behavior is too unstable to keep defending, a sign of a real crack in Republican support.

• Tucker Carlson, who campaigned for Trump, now calls his conduct "deranged" and "too crazy to continue."
• The trigger is Iran policy — Trump posted online about blocking Iranian shipping through the Strait of Hormuz, seen as reckless from a sitting president.
• The broader complaint is that Trump treats a massive military and serious foreign policy like a stream of impulsive social media posts.
• JD Vance is floated as the party's future, but being tied so closely to Trump is seen as a heavy burden for him.

Outlook: Expect more open friction between Trump and parts of his own base as 2028 positioning begins, with Iran policy a likely flashpoint.