By Jordain Carney - 01/27/16 04:59 PM EST
Former Sen. Russ Feingold (D-Wis.), under fire from Republicans on national security, is getting a boost from ex-Defense Secretary Chuck HagelChuck HagelThere's still time for another third-party option Hagel says NATO deployment could spark a new Cold War with Russia Overnight Defense: House panel unveils 5B defense spending bill MORE.
The former Pentagon chief, who stepped down amid tensions with the White House, donated $1,000 to Feingold's campaign during the latest fundraising period, which ended on Dec. 31.
Asked about the donation, Hagel, who previously served as a Republican senator from Nebraska, touted their work together in the Senate.
"[I've] worked with him on many issues. I believe that the Senate needs more senators like Senator Feingold who [will] work across party lines to help govern our country," the former Defense secretary said in a statement to The Hill.
Hagel noted that Feingold's campaign is the only he's donated to so far, but that he "may contribute to other candidates as well."
His donation comes as Senate Republicans focus on national security as they seek to defend 24 seats in the 2016 election.
Republicans lawmakers are increasingly eager to tout their hawkish policy stances in Washington, while linking their Democratic opponents to President Obama on a range of foreign policy and defense issues.
Sen. Johnson, who chairs the Homeland Security and Governmental Affairs Committee, has been a vocal opponent of the Iran nuclear deal, while also offering legislation to crackdown on the acceptance of Syrian and Iraqi refugees.
His campaign and national Republicans have targeted Feingold over a recent interview where he praised Obama's foreign policy and suggested the Iran nuclear deal helped the country avoid a war.
In a statement Tuesday, Johnson's campaign said the Iran nuclear deal "exemplifies the dangerously weak national security record Senator Feingold developed during his 18 years in Washington, and his hypocrisy on special interest money."