Sen. Bernie Sanders told a Senate panel on Tuesday that a constitutional amendment is needed to undo the Supreme Court ruling that let corporations and wealthy individuals spend unlimited sums to sway American elections. Vermont and five other states have adopted resolutions asking Congress for a constitutional amendment to overturn the Citizens United decision. More than 200 local governments, including about 60 towns in Vermont, have passed similar measures. Sanders revealed for the first time that at least 23 billionaire families have contributed a minimum of $250,000 each so far in this year’s campaigns. “My guess is that number is really much greater because many of these contributions are made in secret. In other words, not content to own our economy, the 1 percent want to own our government as well,” he said his appearance before the Senate Judiciary Committee’s Subcommittee on the Constitution, Civil Rights and Human Rights.