It’s not enough, apparently, that some of the wealthiest Americans spend millions to elect their candidates to Congress. Now they are using their fortunes to lobby Congress against any limits on their ability to buy elections.

Koch Companies Public Sector, part of the industrial group owned by a well-known pair of conservative brothers, has hired a big-name firm to lobby Congress on campaign-finance issues, according to a registration form filed a few weeks ago. The form doesn’t say what those issues are, but there are several bills in the House that would reduce the role of anonymous big money in campaigns, and restrict the kinds of super PACs and nonprofit groups that the Koch brothers and others have inflated with cash.

The Senate is also planning to vote this year on a constitutional amendment that would overrule recent Supreme Court rulings and allow Congress and the states to limit donations to candidates, as well as spending on behalf of candidates. Clearly, it’s vital to the Kochs and others like them to prevent such limits from being enacted; their network raised $400 million in 2012, and it has been extremely active again this year. To that end, they have done something ordinary citizens cannot do: They hired the lobbying firm of a well-known former senator, Don Nickles, Republican of Oklahoma, to press their interests. Mr. Nickles started his firm a few months after leaving the Senate in 2005, and he takes in up to $8 million a year from big firms like Exxon Mobil, General Motors and Walmart.

To take one example, the Nickles group has been paid $75,000 every quarter for years by Anadarko Petroleum to lobby on tax and energy issues, including stopping the Close Big Oil Tax Loopholes Act, a Democratic bill that would have repealed $21 billion in tax breaks for energy companies in order to reduce the deficit. (Republicans filibustered it.) That kind of work made the firm the perfect place for the Kochs to take their business, particularly because campaign finance isn’t the only issue they are concerned about. They also hired the firm to lobby on “issues related to the wind energy production tax credit.”