Stanley McChrystal endorsing Alan Khazei, candidate for Kennedy congressional seat

Retired Army General Stanley McChrystal. Alex Wong/Getty Images/file

Retired Army General Stanley McChrystal is endorsing Alan Khazei, providing a boost to the Brookline resident and cofounder of the City Year national service program who is one of five Democrats running to for the congressional seat held by Representative Joseph P. Kennedy III.

The former commander in Afghanistan called Khazei “a model of servant leadership who leads with his values” in a statement put out by Khazei’s campaign, which also noted Khazei is only the fourth candidate McChrystal has ever backed.

“At a time of national division, Alan is exactly the kind of representative we need in the US Congress,” said McChrystal, who has worked closely with Khazei for six years on what is now known as the Service Year Alliance, an effort to make a year of paid, full-time service a common experience for young Americans. McChrystal is the chair of the alliance; Khazei is one of its two vice chairs.

The endorsement could provide some national security cred for Khazei, a graduate of Harvard Law School who has focused his career on organizing youth service. That may prove handy considering one of his rivals in the primary — 31 year-old Jake Auchincloss, a Newton city councilor — is a former Marine Corps captain.

The McChrystal endorsement comes in the wake of some other signs of early strength by Khazei. Earlier this week, he announced that he had raised more than $500,000, and signed up more than 345 volunteers, in the first three weeks of his campaign.

Other Democrats competing in the primary so far are Newton City Councilor Becky Walker Grossman, 39; Jesse Mermell, 39, of Brookline, a former top Deval Patrick aide; and Ihssane Leckey, 34, a self-described democratic socialist from Brookline who was the only one in the race before Kennedy decided to run for Senate.

The race is likely to get even more crowded; pent-up ambition among the state’s Democrats has led many to take a look at running for Kennedy’s seat representing the Fourth District, which stretches from Boston’s western suburbs to the South Coast, including the tony enclaves of Brookline and Newton and the former mill city of Fall River.

Backing Khazei is not the first time McChrystal has gotten involved with a Massachusetts candidate. McChrystal endorsed Representative Seth Moulton’s long-shot primary bid to unseat Democrat John Tierney in a 2014 congressional primary.

The retired general oversaw the US war effort in Afghanistan before he was forced out in 2010 following comments he made to Rolling Stone magazine criticizing the Obama administration.