As billionaire developer Donald Trump became the toast of New York in the 1980s, he often attributed his rise to salesmanship and verve. “Deals are my art form,” he wrote.

But there is `another aspect to his success that he doesn’t often discuss. Throughout his early career, Trump routinely gave large campaign contributions to politicians who held sway over his projects, and he worked with mob-controlled companies and unions to build them.

Americans have rarely contemplated a candidate quite like Trump, 69, who has become the unlikely leader among Republican Party contenders for the White House. He is a brash, Queens-born scion who navigated through one of the most corrupt construction industries in the country to become a brand-name business mogul.

Much has been written about his early career, but many details have been obscured by the passage of time and overshadowed by Trump’s success and celebrity.

(CNN)Donald Trump's glittering empire of New York skyscrapers and Atlantic City casinos have long had a darker side, allegations that the mob helped build them.

Trump's alleged ties to New York and Philadelphia crime families go back decades and have been recounted in a book, newspapers and government records.

"The mob connections of Donald are extraordinarily extensive," New York investigative journalist Wayne Barrett told CNN in an interview.

Barrett, the author of the 1992 unauthorized biography "Trump: The Deals and the Downfall," wrote that Trump's life "intertwines with the underworld."