Sen. Tim Kaine, D-Va., center, speaks to reporters on Capitol Hill in Washington. (Susan Walsh/AP)

Bert Mizusawa, a retired major general in the U.S. Army Reserve and foreign policy adviser to Donald Trump’s presidential campaign, has joined the crowded field seeking the Republican nomination in Virginia for U.S. Senate against Sen. Tim Kaine (D).

Mizusawa is the fifth candidate to jump into the GOP ­primary, set for June.

Republicans running so far include Corey Stewart, the Prince William Board of County Supervisors chair and Trump acolyte who almost won the nomination for governor; outspoken evangelical preacher E.W. Jackson; a two-term state lawmaker, Nicholas J. “Nick” Freitas; and businessman and political newcomer Ivan Raiklin.

Mizusawa, who lives in McLean, ran in the 2010 GOP primary for a House seat in Hampton Roads won by former congressman Scott Rigell.

Mizusawa declined an interview request through his campaign manager, Mike Wade, who said frustration over the recent three-day government shutdown helped motivate him to enter the race.

He already has about $100,000 in commitments from donors and is planning a campaign kickoff later this week, Wade said.

Mizusawa has not met with the National Republican Senatorial Committee, which previously tried to recruit former governor James S. Gilmore III to run.

Wade said Mizusawa is a more credible threat to Kaine than Stewart.

"Résumé. Capabilities. Intellect," he said. "And an ability to actually go forth and have an honest shot at being a challenge to Tim Kaine."

Mizusawa defended Trump’s foreign policy and national defense strategy in an October 2016 column in USA Today.

During the campaign, he served on the same panel of national security advisers that included George Papadopoulos and Carter Page, who are key figures in the probe into Russian interference in the 2016 presidential race.

Wade said Mizusawa has never discussed Papadopoulos or Page with him.

He graduated first in his class at the U.S. Military Academy, attended Harvard Law School and was a MacArthur Fellow in International Security at Harvard’s Belfer Center for Science and International ­Affairs.

“Bert is a longtime friend of the party and was very active in supporting the president in 2016 which is where I first got to know him,” John Whitbeck, chair of the state Republican Party said. “Bert adds an exceptional record of service to an already strong field of candidates.”

Rosalind S. Helderman contributed to this report.