As Donald Trump looks to legitimize his nomination, unique set of problems dog his campaign

Just as Donald Trump is starting to look ahead, his past, it seems, is catching up with him.

A little over one week after Trump all but clinched the Republican nomination with a resounding victory in Indiana, the presumptive presidential candidate is turning his attention to the race for the White House.

But some of his past indiscretions may be slowing him down.

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Hillary Clinton's campaign released a video Saturday morning, attacking Trump over his refusal to release his tax returns — something, the online clip states, every presidential nominee has done since 1976.

Clinton and Democratic rival Bernie Sanders have both released their returns. Before launching his bid, the New York billionaire said he'd do the same if he were to run for office.

On Friday, Trump refused to reveal even the tax rate he pays, saying he would not do so until the IRS finishes auditing his returns. When pressed by Good Morning America, Trump responded: "It's none of your business. You'll see it when I release. But I fight very hard to pay as little tax as possible."

Posing as publicist?

And a two-decade-old bait-and-switch scandal of sorts has emerged, with Trump being accused of previously posing as his own publicist, talking about his love life in phone conversations with reporters at a time when the real estate magnate's relationships were popular tabloid fodder.

The Washington Post unearthed a recording of one such phone call from 1991, with the voice describing Trump as irresistible to women. "He gets called by everybody in the book, in terms of women," says the spokesman, who identifies himself as John Miller. "He's got a whole open field, really."

The Post says it was actually Trump, who denied the claim Friday on the Today show. The Post says he owned up to it at the time.

Also Saturday, the New York Times published an article based on interviews with dozens of women who've worked for Trump or interacted with him in social settings, suggesting a pattern of often unsettling personal behaviour.

Some of the interview subjects recount stories where Trump treated women as sexual objects, making comments about their bodies. But others said Trump encouraged them in their careers and promoted them, sometime to positions in which women tended to be excluded.

Barbara Res, who oversaw construction of Trump's Manhattan business headquarters, said he would sometimes interrupt meetings with comments about women's figures.

During a job interview for a Los Angeles project, for example, Trump made a random aside about Southern California women. "They take care of their asses," Res recalled Trump saying.

Years later, when Res says she had gained weight, she said Trump told her: "You like your candy."

Butler under investigation

Meanwhile, Trump's former butler has drawn the attention of the U.S. Secret Service for threats made online against President Barack Obama.

The Facebook page of Anthony Senecal — who served Trump at his Mar-A-Lago club in Florida — is filled with incendiary comments. In one post from September 2015, Senecal said the military should hang Obama for treason and other "high crimes."

Trump's campaign team has condemned the posts, saying they "completely disavow the horrible statements made by [Senecal] regarding the president and the first family."

Trump has repeatedly come under fire for his missteps during the U.S. primary season, being accused of sexism, racism and being a "brash bully." But he's managed to deflect much of the criticism and continues to draw large, rambunctious crowds ahead of July's Republican convention.

Still, Trump is doing his best to focus on the Nov. 8 presidential election, when he's expected to face off against Democratic front-runner Clinton.

Building bridges

He's been putting in place key elements of his fundraising system — an important undertaking considering a general election campaign can run up to $1 billion US.  

Trump — who says he's "self-funded" his primary race to the tune of $50 million — recently hired a national finance chairman, hedge fund manager Steve Mnuchin, scheduled his first fundraiser, and is on the cusp of signing a deal with the Republican Party that would enable him to solicit donations of more than $300,000 apiece from supporters.

It's an enormous challenge for the wealthy candidate who has campaigned on the fact that he's not beholden to big-money donors and has blasted the political fundraising system as "corrupt."

Trump's campaign has also brought on veteran political operative Paul Manafort as convention manager, appointed New Jersey Gov. Chris Christie as chair of his transition team and floated the idea of a terror commission headed by former New York mayor Rudy Giuliani. On Friday, he picked a prominent climate change skeptic, Representative Kevin Cramer, to help him craft his energy policy.

Trump says he's also narrowed his list of potential running mates down to five or six.

These strategic developments come as Trump was in Washington this week to meet with House Speaker Paul Ryan, RNC Chair Reince Priebus and other top Republicans in the House and the Senate — a series of face-to-face discussions touted as a "positive step" toward unifying the Republican Party.

Ryan had last week said he was "just not ready" to endorse Trump, despite him being the last Republican candidate standing after rivals Ted Cruz and John Kasich dropped out.

But after Thursday's sessions, Ryan, the party's top elected official, appeared to warm to Trump.

"He's been trying very hard to be presidential and gracious and I think he's actually done a nice job of that lately," Priebus said of Trump in an interview with The Associated Press.

A Reuters/Ipsos opinion poll released earlier this week suggested that the election might be more hotly contested than first thought, putting Trump neck-and-neck with Clinton.

The survey found 41 per cent of likely voters would support Clinton and 40 per cent would back Trump, with 19 per cent undecided.