The Dow Jones Industrial Average posted its biggest one-day advance in nearly two months as the potential for regulatory rollbacks injected new enthusiasm for financial stocks.

The stock-market rally Friday snapped the Dow industrials out of a period of sluggish returns. After rallying into the end of 2016, the index’s gains stalled in recent weeks as hopes for rapid movement on increased government spending, corporate-tax cuts and loosened regulation waned.

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