But he will be entering office facing a wave of allegations that he has fabricated a bulk of his resume and filled his profile with bogus claims about his life and career. Questions about his employment history, personal finances, allegations of fraud and whether he lied about the death of his own mother have only continued to mount in recent weeks.
One of these allegations includes a 2008 claim that Mr Santos, then 19 years old, stole a checkbook and was charged with making fraudulent purchases in Brazil.
The New York Times reports that Mr Santos had confessed to the crime at the time, according to local officials.
That year, Mr Santos and his mother were living outside Rio de Janeiro. One month before his 20th birthday, Mr Santos spent nearly $700 at a clothing store using a fake name and stolen checks.
“I know I screwed up, but I want to pay,” he allegedly wrote in a message in 2009 to the store’s owner on Orkut, a Google-operated social media website that is popular in Brazil.
“It was always my intention to pay, but I messed up,” he is recorded as saying.
Mr Santos and his mother appeared before police and admitted his responsibility in November 2010, according to The Times. The next year, a judge ordered his response to the case, but he could not be found when the court tried to subpoena him three months later, The Times reports.
By that time, Mr Santos was already living and working in New York, where he would be elected to represent the state’s 3rd congressional district roughly 11 years later.
“I’m not a criminal,” he told New York-based outlet City & State in an interview last month. “I committed absolutely no crimes. I’m not a wanted criminal in any jurisdiction.”