For years, Fed Chair Jerome Powell responded to President Trump's broadsides in ways that generally avoided escalation. That changed on Sunday night, writes Nick Timiraos.

Core Viewpoint - The Federal Reserve Chair is responding to grand jury subpoenas, indicating a significant legal and regulatory challenge for the institution [1] Group 1 - The Fed Chair spent the weekend deliberating on how to address the subpoenas, highlighting the urgency and importance of the situation [1] - By Sunday, the Fed Chair had reached a decision on how to respond, suggesting a strategic approach to the legal inquiries [1]