That could be changing.
Trump is facing the toughest test of his campaign after a week in which he veered into a series of unexpected controversies and -- for a change -- seemed to struggle in his response. His parade of missteps on issues ranging from national security to abortion have left the Republican front-runner wading through his roughest patch yet on the campaign trail.
Trump will learn whether he dealt his campaign serious damage on Tuesday when GOP voters in Wisconsin go to the polls. Some surveys show Texas Sen. Ted Cruz leading in the primary there and a loss for Trump would make it that much harder to secure the 1,237 delegates he'll need to secure the nomination before the GOP convention.
"I don't know that it's been the worst week of my campaign," he told CBS News in comments that will air Sunday on "Face the Nation. "I think I've had many bad weeks and I've had many good weeks. I don't see this as the worst week in my campaign."
His opponents in the party believe he has already been damaged beyond repair among the broader electorate that will decide the general election.
Tim Miller, senior advisor to the Our Principles PAC, which is dedicated to opposing Trump, believes that the idea that nothing hurts Trump is a "moronic piece of conventional wisdom."
"He has completely turned off huge swaths of the electorate. His numbers have continued to get worse. He would get absolutely massacred on a historic scale (in a general election). All of the data demonstrates it."
The week of staggering developments seems to encapsulate the wild, unorthodox nature of much of the Trump campaign, and the election cycle he has dominated.
It began on Tuesday when his campaign manager, Corey Lewandowski, was charged with simple battery in connection with an incident involving a female reporter. Trump's denial that his aide did anything wrong and his decision to attack Lewandowski's accuser during a CNN town hall raised new questions about his attitude towards women.
During the same town hall, Trump abandoned his earlier pledge to support the eventual GOP nominee if it wasn't him. His Republican competitors, Texas Sen. Ted Cruz and Ohio Gov. John Kasich, also backed off -- reflecting the deep divisions in the party heading into the election.
And he shocked many foreign policy observers with comments suggesting he wants to curb nuclear proliferation while also raising the potential that Japan and South Korea develop such instruments to defend themselves.
Trump set off an even more intense firestorm Wednesday -- and bipartisan anger -- when he suggested women who had an abortion should be punished if the procedure were outlawed. He then changed his line several times on an issue that is viewed as a deeply personal litmus test by many conservatives. On Friday, he again reversed course, telling CBS's "Face the Nation" that federal laws should not be changed
to outlaw the procedure.
Trump also struggled through a highly critical radio interview with radio host Charlie Sykes -- without realizing the well-known Wisconsin conservative was a declared member of the #NeverTrump movement.
Meanwhile, a flurry of news stories emerged about how Trump could harm Republicans in November, with a sudden focus on the fact that if he does not improve his standing, even the wide Republican House majority could be at risk. And Trump caused a new uproar after apparently not being familiar with delegate apportioning rules in Louisiana that could hand Cruz more delegates from the state, even though he walked away with a victory in the primary there.
Trump's Teflon aura
The sequence of events not only tests Trump's Teflon aura but also calls into question his unique method of campaigning, which relies on off-the-cuff calls from the gut, assaults on political correctness and an unusually small-scale political operation around the billionaire.
Trump's defenders believe his message is so in tune with an angry electorate -- and his appeal is so broad -- that his liabilities could evaporate come November, especially against a Democratic candidate with her own high negatives, Hillary Clinton.
"When you get down to a fall election, and the choice is between candidate A and candidate B, then the election always looks different," Trump supporter and CNN contributor Jeffrey Lord said on "New Day." "This kind of thing always happens."
Still, The Washington Post reported this week that Trump would be the most unpopular general election candidate since the paper started polling 32 years ago.
Peter Feaver, a former senior National Security Council adviser in the George W. Bush administration, said that Trump's strength among core supporters has distracted attention away from his liabilities among a wider electorate.
"Trump is the first time in history that we have a candidate who has held onto his supporters so long despite making so many mistakes," said Feaver, now a professor of political science at Duke University.
"He is also the first candidate in history to have been a front-runner for so long without generating any momentum among people who have not already supported him," Feaver said, pointing to the imperative for all potential nominees of widening their political support base and unifying their party behind him.
"That suggests to me that Trump has been hurting himself -- but in ways that are obscured by the unusual fact that they can still hold onto his base."
Trump's tough week came during a lull between primary contests, which meant the narrative of the campaign has, for the first time in a while, not been dominated by his apparent march to the nomination.
In that space, the focus of the media has turned to policy and what Trump would do as president.
At the same time, he's facing more intense cross-examination from journalists. In the CNN town hall, moderator Anderson Cooper dismissed his claim that Ted Cruz started a spat over their wives as the argument of a five-year-old.
Sykes, meanwhile, told Trump in their interview that his row with Cruz was something he would expect from "a 12-year-old bully on the playground, not from somebody who wants the office held by Abraham Lincoln."
And Trump's botched answer on abortion came under intense questioning from MSNBC anchor Chris Matthews.
Taste of scrutiny to come
The showdowns were a taste for Trump of the intense and increased scrutiny and pressure that the billionaire would face during a general election.
And as the political season slips closer toward November, Trump's prospects are coming into focus, as polls show he curtrails both potential Democratic rivals, Hillary Clinton and Bernie Sanders.
Evidence of recent polls suggests that Trump could be digging himself into a hole that might be tough to escape during a general election campaign.
In the latest CNN/ORC poll in mid-March, 73% of female voters said they had a negative view of Trump and just 26% view him positively -- figures that show a significant erosion from data earlier in the campaign.
Those numbers also came before Trump's furious row with Cruz sparked when an unaffiliated super PAC tweeted out a picture of the billionaire's scantily clothed wife and former model Melania. Trump responded by retweeting an unflattering picture of Cruz's other half, Heidi.
Crucially, Trump's standing among Republican women also seems to be eroding. In the latest NBC/Wall Street Journal poll, nearly half of Republican women (47%) said they could not imagine themselves voting for Trump.
That could be a danger sign for Trump in key swing state races in the fall in places like Pennsylvania, Colorado and Virginia, where Republican women in suburban locations could be especially crucial to his chances of being competitive.
As Trump reflects on the events of the last week, it's possible he may conclude that his intimate, loyal campaign operation has left him exposed. For instance, had he been better briefed, or more steeped in the issues, he likely could have avoided the firestorm on abortion.
And it's possible that Trump's contradictions on foreign policy — for instance, saying he is worried about nuclear proliferation but suggesting Japan and South Korea should get nuclear weapons — could have been avoided from organized tutorials with a more robust national security team than the cadre of little-known advisers he has named.
So Trump's tough week could beget an evolution of his candidacy and his political campaign tactics and team.
Failing that, he will need to maintain his unusual political immunity and break the rules that prevail in general elections just as he has rewritten the structure of the GOP nominating race.