WASHINGTON, May 10 -- For years, Donald Trump survived scandals that would have ended most political careers. Impeachments, criminal investigations, civil judgments, and relentless legal scrutiny failed to weaken his grip on Republican voters. Instead, each controversy often deepened his standing among supporters who viewed him as a political outsider fighting an entrenched establishment.

But a widening series of allegations tied to money, influence, and self-enrichment is beginning to create a different political challenge for the White House. Critics across Washington increasingly argue that Trump's expanding web of ethical controversies threatens to overshadow the populist image that fueled his return to power.

The latest controversy...