NEW YORK, United States (AP) — Donald Trump refused on Tuesday to say whether he would accept the election results, injecting new drama into the final day of a turbulent election season.

The Republican presidential nominee also continued to raise doubts about the integrity of the election system, warning of possible voter fraud as his campaign sought an investigation into early voting hours in battleground Nevada.

While familiar charges from an unorthodox candidate, the Election Day statements challenged bedrock principles of American democracy: fair and free elections and the clean transfer of power

They come as Trump eyes a challenging path to the 270 electoral needed for victory, although both sides paint the picture of a very close election that will likely come down to a handful of swing states — Florida, Ohio, North Carolina and Michigan, among them. As the nation’s first polls closed, Trump scored his first victories in reliably Republican Indiana and Kentucky, while Clinton won deep-blue Vermont.

“We’re going to see how things play out,” Trump said on Fox News when asked if he would accept the election results. “I want to see everything honest.”

He offered a similarly non-committal answer earlier in the day as he cast voted in Manhattan. He noted he’s “always concerned” about voter fraud when asked about the issue.

The GOP nominee was joined by his wife, Melania, his daughter Ivanka, his son-in-law Jared Kushner and his granddaughter Arabella while voting at a public school on Manhattan’s East Side. He was booed loudly by onlookers gathered on the sidewalks outside of the school, which had been sealed off with police barricades.

There is no evidence of widespread voter fraud in America.

Such claims have become a regular part of Trump’s warnings of a “rigged election” — a central argument from an outsider candidate who has repeatedly challenged the norms of presidential politics.

Trump’s outsider status has both hurt and helped him over the last year.

His political inexperience allowed him to cast himself as a change agent just as frustrated voters in both parties seemed hungry for change. The message was particularly effective against Clinton, a fixture in public service over the last three decades.

Yet Trump’s inexperience also fuelled a series of self-created controversies, whether a days-long public feud with the parents of a slain soldier or late-night tweet storm citing a beauty queen’s “sex tape.” He insulted opponents from both parties in unusually personal terms, lowering the bar for political discourse in a way never seen before on the national stage.

And he was unwilling to embrace the less-glamorous grunt work that typically defines successful campaigns.

The Republican outsider did little to collect data on prospective supporters. He had no significant staffing presence on the ground in key states. And he refused to invest in a major advertising campaign to keep pace with Clinton.

Ever the showman, his strategy relied almost exclusively on massive rallies to connect with voters. He has filled sports arenas, airport hangars and conference centres from Iowa to Michigan to Florida, often with little notice and little organization.

Trump fell $34 million short of his false boast that he spent $100 million of his own money on his election. Publicly available fundraising reports show he put up about $66 million.

“It was really hard to vote for Donald Trump,” said Debra Sindler of Savannah, Georgia.

The 60-year-old real estate agent said she continued to wrestle with even as she walked to the polls. “I would have never voted for Hillary. And I voted for Donald Trump because I’m concerned about the Supreme Court,” Sindler said.

After voting, Trump spent most of the day behind closed doors, attending a reception with friends and family in the Manhattan skyscraper where he lives and works before heading to a Midtown hotel for his election night party.