Donald Trump. AP Photo/Chris Carlson

He said he wouldn't say it.

But Donald Trump seemingly couldn't resist.

"I wonder if I could say — you know, remember lyin'. Lyin'. I won’t say ‘Lyin' Ted' — I refuse to say it," he told a crowd during a Friday rally in Fresno, California.

“Lyin’ Ted!" Trump then exclaimed. "Holds that Bible high, puts it down, and then he lies. Lyin’ Ted. Well, I’m going to retire that from Ted — I’m not going to call Ted that anymore."

Trump had resurrected perhaps his most infamous moniker to discuss shifting it from Ted Cruz, the Texas senator who challenged him for the Republican nomination, to Hillary Clinton.

But the incident helped illuminate a still-signature part of Trump's campaign rallies: his insults of fellow Republicans.

The Manhattan billionaire is nearly a full month into being the GOP's presumptive nominee, but his rallies over the past week have shown that he doesn't appear to be easing up on fellow Republicans who have drawn his ire.

During a Tuesday rally in New Mexico, for example, Trump unleashed on Susana Martinez, the state's governor. Martinez is the first Latina governor in US history. And she's a Republican.

But all that didn't stop Trump for attacking Martinez — one of a handful of GOP governors who have yet to come out in support of Trump — for not attending his rally.

"We have to get your governor to get going — she’s got to do a better job, OK?" Trump said. "Your governor has got to do a better job. ... She’s not doing the job. Hey, maybe I’ll run for governor of New Mexico — I’ll get this place going. She’s not doing the job. We got to get her moving. Come on. Let’s go, governor."

New Mexico Gov. Susana Martinez. AP Photo/Kathy Willens, File

GOP strategist and commentator Evan Siegfried, who is anti-Trump, wrote on Business Insider the following day that the remark showed Republicans can't trust the real-estate magnate.

He wrote:

A few days ago, Trump’s campaign chairman, Paul Manafort, made it clear to Republicans that if they distanced themselves from Trump, they would not face any retribution. This was a smart move considering how toxic Trump is with every key demographic needed to win an election. Unfortunately, it seems that Donald Trump either did not get the memo or, even worse, he decided to ignore it. The message this sends to other Republicans should be chilling: Trump cannot be taken at his word.

Later in the week, Trump homed in on two of his favorite targets that have said they will not support him: Jeb Bush, the former Florida governor and failed 2016 presidential hopeful, and Mitt Romney, the 2012 GOP nominee.

Claiming that he had "a store that's worth more money" than Romney during a Wednesday rally in Anaheim, California, Trump said if Romney would've decided to run for president in this election cycle "he would've been out quickly."

"I understand losers," Trump said of Romney.

Trump also compared Romney to several animals.

Romney "walked like a penguin around the stage," Trump said.

"He choked like a dog," Trump continued. "You ever see in athletics? He's a choker. And you know the truth, I hate to say it: Once a choker, always a choker. I was nasty about it."

Of Bush, Trump resurrected his "low-energy" label of the one-time 2016 presidential candidate.

"Jeb hasn't done it yet," Trump said regarding Bush endorsing his candidacy. "He will get a burst of energy, and then he will do it. He needs to get up the energy. No, Jeb has not been nice."

In that same Anaheim rally, Trump spent a brief moment discussing the State Department inspector general's report faulting Clinton's email practices, saying it's "not so good."

Donald Trump. Spencer Platt/Getty Images

Tony Fratto, who served as deputy press secretary during the George W. Bush administration, called Trump a "vile creature" when discussing his continued penchant for ripping Republicans.

"Look, I don't whitewash my views on this — I think there's never been a more vile creature to ever run for president than Donald Trump," Fratto told Business Insider in an interview last week. "I think too many people tend to treat him like a normal candidate and look at the things he says and does and tries to find normal explanations for them, but there aren't any normal explanations for them because he's a monster."

"And monsters don't do normal, rational things," he continued.

Fratto said he had "no earthly idea" why he would target Martinez when he needs to improve his standing among both women and Hispanics, groups with which Trump holds distinctly low favorability ratings.

"Because there is no normal idea — there is no normal, rational reason for that," he said. "It is irrational and destructive, and that's why I think ultimately, at the end of the day, that's why he loses."

Last week's NBC News/Wall Street Journal poll found that Trump has consolidated support within the party.

That poll found just 6% of Republicans surveyed said they wouldn't back Trump in the fall, while 86% responded that they'd support the presumptive Republican nominee. An ABC News/Washington Post poll found near identical results.

But Fratto said consolidating the party isn't going to be enough to win, and the constant insults will have to stop for Trump to have a shot.

"We have had the Republican Party unified for multiple elections," he said. "And the truth is we've won the popular vote in exactly one election since 1988. So in the best of times, with the best of candidates, and a unified party, we have a difficult time winning national elections."

He continued:

If you think we're going to win one with a candidate that is intent every single day to divide the party is all you need to know about why he's going to lose. The question for me isn't whether he's going to win or lose — I'm very confident he's going to lose — the question is how much damage is he going to do to the party.

How long will people like me feel like we want to be a part of a party that would nominate someone like him and have to spend all of our time explaining the really ridiculous things that he does.