In his endorsement, Hagel cited their work together as senators for the state as part of the reason he's backing Kerrey.

"He never let political differences get personal," he said of their time in the Senate.

"Leadership is character and courage. Bob has demonstrated both in everything he has ever done. If there ever was a time for Nebraska to send this kind of trusted and experienced integrity to Washington, it is now," Hagel added.

Kerrey has long lagged Republican Deb FischerDebra (Deb) Strobel FischerSenate GOP urges Trump administration to work closely with Congress on NAFTA Defense bill moves forward with lawmakers thinking about McCain Pruitt’s renewable fuel attacks cost him GOP support in Congress MORE in the polls, but an Omaha World-Herald poll out this week put Kerrey just 3 percentage points behind Fischer.

His surge has brought with it an influx of outside spending from both parties, with Republicans attempting to shore up what was once considered a likely win for the party and a necessary seat in their quest to regain a majority in the Senate, and Democrats hoping to buoy Kerrey in the final days.