Washington (CNN) Back in the early chapters of Donald Trump's headline-gobbling campaign, the White House looked upon the spectacle as little more than a diversionary amusement.

Officials tried to stay above the fray, frequently declining to comment with a wry smile, insisting they weren't going to respond to every statement made on the campaign trail.

But as Trump's rhetoric turned to banning Muslims and insulting women, things began to change, leading to a series of statements in which the President of the United States flatly said the Republican front-runner was unqualified to be commander in chief.

By the end of last summer -- as Trump was saying that African-Americans were worse off under President Barack Obama -- the President himself began dipping a toe in.

"America is great right now," he said in September. "America is winning right now."

No names mentioned. None needed.

JUST WATCHED President Obama: I believe Trump won't be president Replay More Videos ... MUST WATCH President Obama: I believe Trump won't be president 00:53

Within weeks, the White House's own language started to ramp up. "We betray the efforts of the past if we fail to push back against bigotry in all its forms," Obama said at a ceremony commemorating the abolition of slavery . "Our freedom is bound up with the freedom of others. Regardless of what they look like or where they come from, or what their last name is, or what faith they practice."

That might not sound specific. But coming just after Trump proposed temporarily banning all Muslims from entering the U.S., everyone knew exactly what Obama was referencing.

At the time, the White House said Obama was merely expressing American values.

White House Press Secretary Josh Earnest, however, was far less opaque, unleashing a string of invective against the GOP front-runner at a White House briefing. Terms like: disqualifying, vacuous, lies, deeply offensive, harmful, toxic, corrosive, incendiary, grotesque, morally reprehensible, contrary, farfetched, unrealistic and counter to the Constitution.

And for a final, stinging slap: a joke about Trump's hair, calling it, and Trump's general appearance, "outrageous."

"The Trump campaign for months now has had a dustbin-of-history-like quality to it. From the vacuous sloganeering to the outright lies to even the fake hair, the whole carnival-barker routine that we've seen for some time now," Earnest let loose. "The question now is about the rest of the Republican Party and whether or not they're going to be dragged into the dustbin of history with him. And right now, the trajectory is not good."

"Disgusting," Trump quickly shot back.

Taking on Trump

Since then, the administration -- even the President -- has hardly been shy about wading into that very muckfest it originally vowed to avoid.

"Vulgar and divisive," Obama declared of the politicking last month. "Damaging," Earnest has said. Saying that the Republican rhetoric (read: Trump's) was potentially hurtful to both national security and America's standing abroad.

Said Obama at a St. Patrick's Day event: "In America, there is no law that says we have to be nice to each other, or courteous, or treat each other with respect. But there are norms. There are customs. There are values that our parents taught us and that we try to teach to our children to try to treat others the way we want to be treated."

"Neither President Obama nor President (George W.) Bush would tolerate someone on their staff being accused of physically assaulting a reporter, lying about it and then blaming the victim," he stated emphatically in a White House briefing. He added, "Nobody is particularly surprised that's a behavior that Mr. Trump doesn't just seem to tolerate, he seems to encourage."

So it wasn't much of a surprise on Friday when Obama essentially again told the world that Trump isn't fit to be President, speaking at a news conference following the Nuclear Security Summit in Washington. This time, Trump had attracted controversy by suggesting earlier in the week that it may be time for Japan and South Korea to develop their own nuclear arsenals so the U.S. can pull back from Asia.

"The person who made the statements doesn't know much about foreign policy, or nuclear policy, or the Korean peninsula -- or the world generally," said Obama, who didn't mention Trump by name.

JUST WATCHED Donald Trump: I would've beaten Obama in 2012 Replay More Videos ... MUST WATCH Donald Trump: I would've beaten Obama in 2012 00:47

That wasn't the case in February, when Obama used another news conference to deliver perhaps his most scathing, extensive Trump slam

"I continue to believe that Mr. Trump will not be president," Obama said. "And the reason is because I have a lot of faith in the American people. And I think they recognize that being president is a serious job. It's not hosting a talk show or a reality show. It's not promotion. It's not marketing. It's hard," adding, "It's not a matter of pandering and doing whatever will get you in the news on a given day."

Obama continued: "So yeah, during primaries, people vent and they express themselves ... but as you get closer, reality has a way of intruding. And these are the folks who I have faith in, because they ultimately are going to say, whoever is standing where I'm standing right now has the nuclear codes with them, and can order 21-year-olds into a firefight, and (has) to make sure that the banking system doesn't collapse, and is often responsible for not just the United States of America, but 20 other countries that are having big problems, or are falling apart and are gonna be looking for us to something."

"The American people are pretty sensible," Obama continued. "And I think they will make a sensible choice in the end."

So far, however, none of the White House's swipes have seemed to land, at least not to make a dent in Trump's support. And the candidate himself wasn't intimidated when Obama took him on in February.

"This man has done such a bad job," Trump said in response. "He has set us back so far, and for him to say that is a great compliment, if you want to know the truth."