Republican front-runner Donald Trump was well ahead in early voting in Indiana on Tuesday in what could herald an important victory that would move him close to being unstoppable in his march to the party's presidential nomination.
Democrat Hillary Clinton also took an early lead over Bernie Sanders in the voting shortly after a first wave of polling stations closed at 6 p.m. EDT. Other voting places were to close at 7 p.m. EDT.
With 1 percent of the votes counted, Trump led with 52.6 percent of the tally to 28.7 percent for U.S. Senator Ted Cruz of Texas and 12 percent for Ohio Governor John Kasich.
Clinton led with 63 percent of the vote to 37 percent for Sanders.
Cruz has been counting on a win in Tuesday's primary to slow the New York businessman's progress toward the nomination.
But polls in recent days have shown Trump opening up a substantial lead in the Midwestern state over the senator.
Campaigning in Evansville, Indiana, Cruz sounded deeply frustrated by the bombastic real estate mogul, who has ripped conservative Cruz at every turn.
"The man cannot tell the truth but he combines it with being a narcissist," Cruz said of Trump, "a narcissist at a level I don't think this country has ever seen."
Cruz's fury was set off by Trump saying in a television appearance that the senator's father, Cuban emigre Rafael Cruz, was linked to John F. Kennedy's assassin, Lee Harvey Oswald. Trump was referring to a report by National Enquirer, a supermarket tabloid known for celebrity gossip and alien sightings.
Cruz also termed Trump a "serial philanderer" -- likely as part of his strategy to try to siphon the support of evangelical voters from Trump.
Republican voters in Indiana could give Trump an almost unstoppable advantage in his turbulent journey toward the party's presidential nomination. He holds a double-digit polling lead in the state.
Trump, who frequently refers to Cruz as "Lyin' Ted," quickly responded to his rival's attack.
"Over the last week, I have watched Lyin’ Ted become more and more unhinged as he is unable to react under the pressure and stress of losing, in all cases by landslides, the last six primary elections --- in fact, coming in last place in all but one of them," he said in a statement.
(Additional reporting by Alana Wise in Indianapolis and Ginger Gibson in Terre Haute and Doina Chiacu and David Alexander in Washington; Writing by Steve Holland and James Oliphant; Editing by Alistair Bell and Andrew Hay)