Overall, 29 members of the House and Senate own at least some Berkshire stock, but only five have more than $100,000 worth, according to the Center for Responsive Politics. Nelson and his wife own $1.5 million to $6 million worth of the stock, according to his most recent financial disclosure report. Sen. Tom Harkin, D-Iowa, has between $1,000 and $15,000 worth. No other Midlands representatives listed Berkshire stock on their disclosure forms.

Berkshire also is Nelson's top campaign contributor, according to the Center for Responsive Politics, with employees and its political action committee donating $75,550 over his Senate career.