Deal Boom Under Threat in Washington as Aon Tie-Up Dies (2)

With a new appetite for stepped-up antitrust enforcement sweeping Washington, big deals are already getting harder to do.

Aon Plc’s decision on Monday to abandon a $30 billion takeover of insurance brokerage Willis Towers Watson Plc after Justice Department pushback is the latest signal that transactions that consolidate industries could run into trouble.

The Justice Department in a statement said that the deal would have consolidated the insurance brokering industry from three big competitors to two.

“This is a victory for competition and for American businesses, and ultimately, for their customers, employees and retirees across the country,” Attorney General ...