As a life-long politician, Tom Daschle never earned much money. But he retired from the Senate, after being defeated for re-election by John Thune, as a multimillionaire. He retired to Georgetown, of course, not to South Dakota. This happens a lot in Washington, and Daschle's case is pretty typical.
His wife Linda is or was a lobbyist, and she was the one who reported the family's income. (This is inference, since Daschle consistently chose not to make his tax returns public.) Linda Daschle made millions "lobbying" on behalf of various corporate interests. There was no conflict of interest, the Democrats assured us, because Linda Daschle only "lobbied" the House of Representatives, not the Senate, where her husband was either the Majority or the Minority Leader for much of his career.
But wait! If a company hired Linda to lobby House members, the check they wrote went straight into the Senate Majority Leader's joint checking account.