3M Plumbs the Depths of the Dow as Billions in Legal Costs Loom

3M Co.’s first-quarter plunge is scaring off even the bravest of dip buyers as its crippling legal troubles continue to haunt the century-old industrial giant.

Shares of the company — whose products encompass everything from auto parts to Post-it notes — are down 14% in the first quarter, making them the biggest decliners in the Dow Jones Industrial Average. And only 51 of the 503 companies in the S&P 500 Index have had worse performances than 3M this year.

“This stock is currently uninvestable,” RBC Capital Markets analyst Deane Dray said in a phone interview. “It is going ...