President Trump likes to taunt his enemies but he seems to have a special place in his Twitter thumb for Sen. Richard Blumenthal, the Connecticut Democrat who was talking about the Russia investigation on CNN on Monday morning.
Trump has mentioned Blumenthal in at least four other tweets, on two separate dates since February, according to the Trump Twitter Archive.
Each time, Trump has maligned Blumenthal for misrepresenting his military service during the Vietnam War, an ironic line of attack from a president who received five deferments from the draft and never served in uniform.
Trump's lack of military service is not unique in the White House.
Presidents Clinton and Obama never served in uniform, and President George W. Bush sparked controversy with his service in the Texas Air National Guard during the Vietnam era. He was not deployed abroad.
President Reagan spent most of World War II in California, where he produced training films for the Army Air Forces. President George H.W. Bush, a Navy pilot, was shot down in World War II, and Presidents Ford and Carter both served aboard ships in the Navy.
None of those presidents called out others for their service, however.
Trump called Blumenthal a "phony Vietnam con artist" in one tweet Monday and said he "defrauded voters" in another. In February, he accused Blumenthal of a "major lie" on the subject. In May, he alleged Blumenthal committed "one of the greatest military frauds in U.S. history."
"Interesting to watch Senator Richard Blumenthal of Connecticut talking about hoax Russian collusion when he was a phony Vietnam con artist!" Trump tweeted Monday.
Indeed, Blumenthal was forced to apologize in 2010 for saying he had served in Vietnam, when in fact he served in the Marine Corps Reserves during the period and was not deployed abroad.
Trump's own military history has come up before, including during his public feud with the Muslim family of a fallen soldier after the 2016 Democratic National Convention.
During the Vietnam War, Trump got four draft deferments for being a college student that allowed him to avoid compulsory military service.
After that, he received a fifth deferment for bone spurs in his heels. He called the condition "temporary" and "minor" in an interview last year with the New York Times.
"I had a doctor that gave me a letter — a very strong letter on the heels," he said.
In a 2015 press conference, Trump forgot which heel had been diagnosed, before his campaign clarified that it was both of them.
Blumenthal, for his part, claimed the president's "bullying" on Twitter was not getting to him.
"This issue isn't about me," he tweeted. "It's about the Special Counsel's independence and integrity," referring to the investigation led by Robert S. Mueller III into whether the Trump campaign cooperated with Russian interference in the 2016 campaign.
Trump got in the last jab, or the last tweet anyway.
"I think Senator Blumenthal should take a nice long vacation in Vietnam, where he lied about his service, so he can at least say he was there," he wrote later.