Riggs, a 68-year-old Republican, called his critics punks and cowards, challenged them to compete against him in the gym, and accused them of denigrating his military service.
Hours earlier, his Democratic rival Kathy Hoffman had declared victory, although no news outlets have called the contest yet. At the moment, the results from Tuesday's election show her leading Riggs by 46,700 votes, although approximately 220,000 ballots remain to be counted.
When Phoenix New Times reached out to Riggs for comment on Monday morning, he did not respond. He then proceeded to delete the tweets posted on Sunday night, and briefly deactivated his account.
In a follow-up text message, Riggs wrote, "Please do not contact me. You are not authorized to use or share my mobile number. Please acknowledge receipt of this request."
On Sunday evening around 8:30 p.m., Riggs seemed to fly off the handle after reading a tweet from a local political consultant, David Leibowitz, who took a jab at Riggs for his perennial campaigning – Riggs previously sought the Republican nomination for Senate in California and governor of Arizona, losing both times with disappointing results.
"You & your pasty ilk are welcome to join me @ 5 am for one of my daily workouts. Can you do a pull-up yet?” -Frank Riggs
Leibowitz suggested that Riggs might run for Corporation Commission next after his loss to Hoffman. (Unbeknownst to him, Riggs actually floated a run for the commission in 2016.)
"Thanks for the tweet on #VeteransDay, you gutless punk," Riggs replied on Sunday. "Let me know if you ever wear the uniform, run for office, or serve in any capacity. All I did was protect the likes of you.
An Army veteran, Riggs took offense at receiving criticism on Veterans Day.
"Gutless punk? Coward?" Leibowitz replied. "You sure do love name-calling. And you wonder why you keep running and losing? I had no idea you’d served in the military. I admire that about you. All the rest? I’ll refrain from further jabs at your tender ego."
After some more back-and-forth with Leibowitz, Riggs roped in two other prolific Twitter users and PR types, attorney Thomas Galvin and Barrett Marson, with whom he apparently has beef.
“Punk & coward. Couldn’t last one week in boot camp or police academy. Sorry Softie," Riggs told Leibowitz. "@ThomasGalvin @barrettmarson Does this shoe fit you too?”
Riggs has acquired a reputation for his hair-trigger Twitter responses to critics. Last month, he also used an offensive, outdated term when he described working with "Oriental" police officers during his career as a cop.
A three-term California congressman during the 1990s, Riggs moved to Scottsdale in 2002 after leaving Congress and worked in charter school finance and development. He narrowly clinched a victory in Arizona's crowded five-person Republican primary for superintendent, unseating incumbent Diane Douglas.
In no particular order, here are a few other things that Riggs said during his 15-tweet tirade, which continued past 10:15 p.m.
Leibowitz suggested that they could settle their grudge by Indian leg wrestling or a steel cage match, if Riggs weren't 68 years old.
Arizona Mirror editor-in-chief Jim Small wrote on Twitter that Leibowitz had possibly surpassed a New Times reporter's position on Riggs' "shit list." In response, Riggs wrote, "Just another punk comment by a softie who would never serve but can sit in judgment of those who do. Objective journalism on social media."
Riggs then suggested that Small ought to apologize "for the cheap shots on #VeteransDay," and referred to excuse-making by people who haven't enlisted.
"I've heard every excuse from the sniveling," Riggs wrote.