A high-stakes political clash between billionaire entrepreneur Elon Musk and former U.S. President Donald Trump has sent ripples through both Wall Street and Silicon Valley. Musk admitted on Wednesday that he regrets several social media posts made during last week’s public feud with Trump, his one-time political ally. The fallout has already impacted Tesla Inc. $TSLA and cast doubt on future public-private collaborations under a potential second Trump administration.