Saturday was a day of reckoning in the 2016 US presidential race.

Donald Trump, the billionaire mogul and former reality show host, easily rode to victory in the Republican primary election in South Carolina, solidifying his lead and making it ever more likely that he will become the party's nominee.

In a victory speech held before an audience of cheering supporters, Trump lauded his family while slamming everything from Mexico to the US education system to Barack Obama, whom he called "a political hack."

Meanwhile, he saved some faint praise for his opponents, including Texas Senator Ted Cruz and Florida Senator Marco Rubio, as they battled their way through an increasingly challenging nomination race.

"It's tough, it's nasty, it's mean, it's vicious," Trump said of the campaign. "It's beautiful."

Battle for second place

The spotlight was not only on Trump, though: Observers were also careful to watch Cruz and Rubio, who were neck and neck for second place.

"After tonight, this has become a three-person race and we will win the nomination," Rubio told his audience following the results, which put him just ahead of Cruz.

Meanwhile, former Florida governor Jeb Bush - once the assumed frontrunner - announced his decision to suspend his campaign. His announcement was met with scattered cries of disapproval as he urged the need for a president who was "a servant, not a master."

Hillary takes Nevada

In the Democratic caucuses in Nevada, former Secretary of State Hillary Clinton managed a slight victory over Vermont Senator Bernie Sanders, despite initial speculation Sanders might pull ahead.

"Some may have doubted us, but we never doubted each other," she told an audience of cheering supporters shortly after the results were announced. "This one is for you."

Nevada was seen as a necessary victory for Clinton, who has been faced with a stiff challenge from Sanders. Before voting started, the Clinton team visited Las Vegas to speak with Latino voters, who form a key part of Clinton's base.

Sanders, meanwhile, reiterated his commitment to stay the course and take the fight to the Democratic National Convention.

blc/bw (AP, AFP, dpa, Reuters)