Former labor union leader and independent candidate Dan Osborn has announced his bid for a Nebraska U.S. Senate seat, challenging Republican Sen. Pete Ricketts.

Independent Dan Osborn announced another bid to represent Nebraska in the Senate on Tuesday, challenging GOP Sen. Pete Ricketts after his loss in an unexpectedly competitive race against a Republican incumbent last year.

Will Coup, a campaign spokesperson for Senator Pete Ricketts, told the Nebraska Examiner: "Senator Ricketts has consistently worked for and voted to secure the border and cut taxes for Nebraska workers, families and seniors. Dan Osborn is bought and paid for by his liberal, out-of-state, coastal donors."