John Fund‘s latest column at National Review Online examines the degree to which Republican presidential nominee Donald Trump is willing to work for his White House bid.

Donald Trump does know how to act in a serious, restrained way that impresses people. The fact that he isn’t displaying those qualities in his presidential race raises questions about just how much he cares about winning.

There was a time when he really cared about the art of one deal. In 1990, Trump nearly went bankrupt and was forced to ask dozens of banks to whom he owed $4 billion to change the terms on their loans and forgive some of his debts. In describing this deal, Trump has said he focused on it with more intensity and purpose than anything he’d done in his life to that point. …

… But Trump isn’t acting with that seriousness of purpose now. He blew off holding traditional practice sessions before the first debate last week — and it showed. Then he spent days counter-punching against Alicia Machado’s accusation that Trump had humiliated her 20 years ago over her weight gain shortly after she was crowned Miss Universe. Trump’s heated back-and-forth with Machado and her supporters in the Clinton camp culminated in a tweet storm at 3 a.m. on Friday in which he urged followers to check out her “sex tape.” (She appeared in a controversial reality show on Spanish TV that seemed to show her having sex under cover of blankets.) Tweets about how exactly he would help average Americans or “make America great again” have been scarce of late. Despite warnings that he should cool it, Trump proceeded on Friday to imitate Hillary Clinton buckling at a 9/11 memorial service last month and suggested she might not have been “loyal” to her husband.

All this juvenile behavior has caused Trump to slump in polls. Fox News found that after the first debate, 67 percent of likely voters said Hillary Clinton had the temperament to serve as president. Trump’s temperament number fell a point to 37 percent — a 30-point gap.