Presidential candidates facing defeat often try to change their image.

Vice President Hubert Humphrey broke with President Lyndon Johnson and called for halting U.S. bombing in Vietnam. Moderate centrist Al Gore sought to turn himself into a raging populist. President George H.W. Bush took to hurling verbal epithets at his rivals. And Bob Dole started condemning press failure to spotlight Bill Clinton’s shortcomings, thundering daily, “Where is the outrage?”

All still lost.

Now, trailing Hillary Clinton in almost every key state, Donald Trump is changing the tone — but not the essence — of his outsider presidential campaign. After spending 14 months spewing verbal venom and denigrating ethnic groups and rivals, Trump has abruptly, but imprecisely, expressed regret if his words hurt anyone, lowered the boisterous tone of his speeches and tempered some of his most controversial positions.

He’s presumably trying to convince voters that, contrary to current attitudes, he has the proper temperament to be president. A lot will depend on whether Trump is able to maintain his new tone and, if he can, convert enough skeptical voters.

Even before this, Trump stopped referring explicitly to his oft-stated vow to ban all Muslim immigration to the United States. Instead, he talks of requiring “extreme vetting” of immigrants from areas where terrorism is rampant, presumably stiffening the lengthy checks now being made.

Though he made a strict immigration policy a cornerstone of his campaign from the very first day, including promising to forcibly deport millions who are here illegally, he now seems to be leaving open the possibility of modification. Asked Sunday on CNN’s State of the Union if Trump was changing the forced deportation plan amid rumors he signaled a change to his Hispanic advisory group, new campaign manager Kellyanne Conway replied, “To be determined.”

Meanwhile, though Trump has yet to address any African-American audiences (among whom polls show he has virtually no support), he started stressing the “deep personal importance to me” of helping African-Americans. He said he wants to make the GOP again the party of Abraham Lincoln, declared Clinton “would rather provide a job for a refugee from overseas” than for an African-American youth, and asked African-Americans — while addressing a mainly white suburban Michigan audience — “What the hell do you have to lose?”

So far, this “new Trump” has been mostly rhetorical. He has made no explicit apologies to those he assailed: the Mexican-American judge whose heritage he lambasted, the Gold Star family whose motives he questioned and the journalist whose disability he mocked. He still blames President Barack Obama and Hillary Clinton for creating the Islamic state and still makes unsupported promises of lowered energy bills, factories sprouting coast-to-coast and a sharp drop in crime.

By contrast, he said Saturday in Fredericksburg, Va., a Clinton presidency would cost “your jobs … your wages … your medical. You’re going to lose everything.”

Trump supporters and some who know him contend the lowered volume and less bombastic language represents the real Trump, not the persona he adopted for political purposes. His goal, many analysts agree, is aimed less at attracting support from minorities than at regaining lost support among moderate GOP suburbanites.

“I have always been the same person,” Trump tweeted recently, adding “it would be very dishonest to supporters” for him to change now.

But voters could be forgiven if the last week left them baffled about what was real and what was not — and which Trump they would get as president. Their conclusion may determine if he can give Clinton a run for her money in the campaign’s home stretch.

The reason is that Trump’s tone has been a significant factor in the public’s judgment that, so far, he has not shown the temperament to be president. In last week’s NBC News Survey Monkey weekly tracking poll, only 17 percent agreed Trump had the personality and temperament to serve, including barely more than one-third of Republicans, compared with Clinton’s 42 percent.

But tone is not Trump’s only problem. Another is the sense, underscored by his consistent avoidance of details and his frequent misstatement of facts, that he lacks knowledge about government in general and the specific issues he would have to handle as president.

The forthcoming presidential debates will test both factors. They remain Trump’s best chance to show who he really is and what he would do as president, and to overcome the underlying doubts of many voters.

Carl P. Leubsdorf is a columnist for The Dallas Morning News. Readers may email him at carl.p.leubsdorf@gmail.com.