Lockheed Martin gets about 70% of its sales from the U.S. government. Medicaid accounts for three-quarters of Molina Healthcare's premium revenue . Coinbase is waiting on Congress to finish writing the rules for cryptocurrency .

For some of the biggest U.S. companies, Washington is part of the business model. Now, the midterm election could change who holds the leverage.

A Democratic victory in either or both chambers of Congress would grant the party new leverage to investigate companies , challenge federal spending and demand legislative concessions. But their reach would have limits: President Donald Trump would retain his veto and broad authority over tariffs, immigration and federal regulation.

Historically, stocks have performed well under divided government. Under Republican presidents, the S&P 500 has gained an average of 23% in the year after midterms when Congress was split, compared with 16% when Democrats controlled both chambers, according to a Morgan Stanley analysis published Thursday.…