Todd Gitlin is a professor of journalism and sociology and chair of the Ph.D. program in communications at Columbia University.

The constant spotlight fixed on Donald Trump for the last year would have overwhelmed any other candidate, particularly one so evasive. But not him: Trump now campaigns as pro-life — but he was “very pro-choice” well into his 50s; he boasts that he’ll defeat the Islamic State “very, very quickly,” but won’t specify how; he claims he’s worth billions, but won’t release his tax returns. He became the GOP’s presidential nominee without revealing anything approaching a clear picture of his mind or his history. How’d he do it?

He cracked campaign reporters’ code. And if they don’t want to get rolled again in the general election, journalists have to change tactics.

Early in this campaign season, Sunday morning network news hosts granted Trump the special prerogative of phoning in for interviews, off camera, making it impossible to know, in real time, if he was consulting notes or advisers during interviews. And because of an early polling lead based in large measure on his near-universal name recognition, Trump was center-stage getting most of the air time during every GOP primary debate.

In those debates, and in interviews, Trump regularly runs circles around interviewers because they pare their follow-up questions down to a minimum, or none at all. After 30-plus years in the media spotlight, he knows how to wait out an interviewer, offering noncommittal soundbites and incoherent rejoinders until he hears the phrase, “let’s move on.” He takes advantage of the slipshod, shallow techniques journalism has made routine, particularly on TV — techniques that, in the past, were sufficient to trip up less-media-savvy candidates — but that Trump knows how to sidestep.

The Republican presidential front-runner reversed course on a whole load of issues – all on May 4. (Peter Stevenson/The Washington Post)

MSNBC’s Joe Scarborough and Mika Brzezinski regularly host Trump, but almost never interrogate him. Recently, in off-air banter during a “Morning Joe” commercial break, Brzezinski called a portion of one of Trump’s rallies a “wow moment,” to which Trump replied, “You have me almost as a legendary figure. I like that.”

When they do get around to questioning him, it tends to go like the Feb. 18 televised town-hall appearance where Trump insisted: “I said the [Iraq] war is a disaster because you’re going to destabilize the Middle East. I said it long before 2003 … I’m the only one that said don’t go in and I said it in 2003, I said it in 2004. … There’s headlines and magazines. Don’t go into the war.” To this, Scarborough reasonably asked, “So where did you say this?” But Trump was able to wriggle away with this nonresponse: “I said it all over the place. It’s written all over the place, Joe — 2003, 2004 headlines and articles.” To which Scarborough threw in the towel: “OK.” Whatever Scarborough’s recent criticism of Trump, in The Post and via Twitter, on his own TV show he’s been a softie.

Then there’s CNN’s Wolf Blitzer. In a Jan. 7 interview breathlessly touted as an exclusive one-on-one, Blitzer let Trump get away with a hysterical warning about the national debt jumping, imminently, to $21 trillion, without questioning it. (Many sober analysts, including Fortune’s Stephen Gandel, have deplored the “long-running hysteria around the national debt.”) But Blitzer immediately turned to the subject of Saudi Arabia. Rambling in response, Trump said of Iran: “They want to take over Saudi Arabia.” Again, no follow-up from Blitzer after Trump paused his soliloquy.

During the Oct. 28 Republican debate, CNBC’s John Harwood substituted snark for serious inquiry. When he asked Trump if he was running “a comic book version of a presidential campaign,” Trump rightly chided him, then quickly changed the subject to a comic book answer, blathering on about how easy his Mexican wall would be to build, because “they built the Great Wall of China, that’s 13,000 miles.” Both the question and the answer are nearly useless to voters, but if Harwood was going to go that route, couldn’t he have followed up by noting that the Great Wall probably took centuries to build, at a cost of what some experts say was hundreds of thousands of lives? That might at least have pushed Trump to acknowledge the magnitude of the undertaking he’s proposed.

Right after that same debate, Trump boasted to CNBC’s Joe Kernen, “My relationship with Hispanics is incredible.” Though polls consistently show the opposite, Kernen failed to broach any evidence to the contrary. Trump told him, “The single greatest rip-off of our country is through currency manipulation by Japan, by China, by everybody, Joe” — another point he’s made over and over on the campaign trail. Kernen, though, apparently wasn’t prepared to note that the International Monetary Fund disagrees: “Since 2015, the People’s Bank of China, the central bank, hasn’t been keeping the currency cheap. Rather, it’s been defending the yuan, drawing down its foreign-exchange reserves in order to keep the value aloft.”

To be “fair and balanced,” if you will, consider also Fox News. In December, on the subject of Trump’s desire to halt Muslim immigration, Chris Wallace puckishly asked if it would take “Donald Trump years as president to be able to sort out the good Muslims from the bad Muslims.” But at other times, Wallace has gone hopscotching for one-liners, without follow-up, and Trump has obliged. In October, Wallace asked: “Would you be willing to use the debt limit and risk the possibility of the country going into default to get more spending cuts?” Trump’s response: “I want to be unpredictable, because, you know, we need unpredictability. Everything is so predictable with our country.” Wallace changed the subject.

Trump is a master of darting from slogan to slogan. That’s why interviewers must do their homework and be prepared to go at least 2-3 questions deep on any issue.

When Trump makes a blunt, sweeping statement like saying he’d “get along very well” with Russian President Vladimir Putin, journalists have to follow up by asking how, specifically, he thinks Putin would respond to increased economic sanctions. If he won’t answer, they should do what conservative Wisconsin talk radio host Charlie Sykes did back in March. Interviewers should say, flatly, “You’re not answering my question.”

Reporters at major news outlets need to inquire more deeply into Trump’s alleged business relationships with mafia-controlled construction companies, and about the way he cut corners to get lavish taxpayer subsidies and government approvals for his hotels and casinos — questions that still lack complete answers since they were raised in Wayne Barrett’s 1992 book, “Trump: The Deals and The Downfall,” and further developed by Pulitzer Prize-winning journalist David Cay Johnston.

Journalists need to remind Trump, and voters, of the many times he’s claimed as fact something demonstrated to be false — that on 9/11, for example, “thousands and thousands of people” in New Jersey Arab American communities cheered the destruction of the Twin Towers. If Trump says he can’t remember, remind him he claimed to have “the world’s greatest memory.”

It is possible to hold Trump’s feet to the fire. You have to be resolute and persistent.

Tom Wright of Brookings unpacked the history behind Trump’s retro foreign policy platform. The Post’s Robert O’Harrow reported in-depth on Trump’s failed casino ventures. For 2015, PolitiFact made Trump’s aggregated campaign misstatements their “Lie of the Year.” In a few instances, reporters have done it right.

But more often, it looks like interviewers are on a tight leash — maybe because their bosses are blinded by ratings. CBS President Leslie Moonves recently said of the Trump phenomenon: “It may not be good for America, but it’s damn good for CBS.” His admission was both refreshing and revolting in its candor — and goes a long way to explaining why, according to one survey, through February, Trump scored almost $2 billion worth of free media this cycle — about as much as all other candidates together. It poses most acutely a question that goes to the soul — battered as it may be — of journalism. Is the mission to elicit facts and evaluate claims, or to dash off, hell-bent, in the ratings chase? It should be obvious.

The general election is upon us. There won’t be any do-overs. It’s time for journalists to honor the good name of their profession and take off the kid gloves. If they don’t put down their softballs, if they don’t stop letting simple-minded questions substitute for serious exploration, they’ll share responsibility for enabling — and helping elect — President Donald J. Trump.