Front-runner Donald Trump said on Sunday that he will have essentially sealed the Republican U.S. presidential nomination if he wins Tuesday's contest in Indiana, where he now holds a big lead over chief rival Ted Cruz.
A new NBC/Wall Street Journal/Marist opinion poll showed Mr. Trump with a wide lead in Indiana, 49 percent to 34 percent for Cruz and 13 percent for a third candidate, Ohio Governor John Kasich.
Trump, a 69-year-old real estate developer, sounded confident in an interview on "Fox News Sunday" when asked whether Indiana would basically end the long-running Republican race in his favor.
"Yes, it's over," Trump said. "It's already over."
The poll showed the depth of the challenge facing Cruz, a conservative U.S. senator from Texas who is trying to prevent Trump from winning the 1,237 delegates needed to seal the nomination.
Cruz's hopes rest on emerging as a consensus alternative to Trump at the Republican National Convention in Cleveland on July 18-21. Former U.S. Secretary of State Hillary Clinton, 68, leads U.S. Senator Bernie Sanders, 74, of Vermont in the race for the Democratic nomination.
Trump, who has amassed 996 delegates, according to an Associated Press count, has momentum behind him and looks increasingly likely to win the nomination outright, without a contested convention, perhaps when California votes on June 7.
Indiana has 57 Republican delegates. Three are awarded from each of the state's nine U.S. congressional districts with the candidate who receives the most votes taking them all. The 30 others are awarded to the candidate who wins the most votes statewide.
On NBC's "Meet the Press," Cruz said he has momentum in Indiana based on his choice of former candidate Carly Fiorina for his vice president and Friday's endorsement by Indiana Governor Mike Pence.
"I think the support we are seeing is surging," Cruz said.
Cruz, 45, was pressed on whether he would support Trump if the New York billionaire is the Republican nominee. Cruz evaded the question each time and turned the questions into an attack on broadcast media.
"I recognize that many in the media would love to see me surrender to Donald Trump because that means that Hillary wins. The media has given $2 billion in free advertising to Donald Trump," Cruz said.
Americans will elect a successor to President Barack Obama on Nov. 8.
CLINTON URGES SANDERS QUIT
On the Democratic side, front-runner Mrs. Clinton told CNN's "State of the Union" that rival Bernie Sanders has been "helpful" in bringing millions of people into the party's presidential race, but it was time for him to step aside.
"There comes a time when you have to look at the reality," said Clinton, who won four of the five Northeastern states that voted last Tuesday and who has a big lead in the delegate race ahead of the Democratic National Convention in Philadelphia on July 25-28.
Clinton, the wife of former President Bill Clinton and a former U.S. senator from New York, waved off Trump's attacks on her. Trump has said Clinton would be getting little support if she was not a woman.
"I have a lot of experience dealing with men who sometimes get off the reservation in the way they behave and how they speak. I'm not going to deal with their temper tantrums or their bullying or their efforts to try to provoke me. He can say whatever he wants to say about me. I could really care less," Clinton said.
Obama, appearing at his last White House Correspondents Association annual dinner on Saturday, savaged Trump for his foreign policy views, joking that he had learned from Miss Sweden and Miss Argentina from his years operating the Miss Universe competition.
A former reality TV show host, Trump said in his Fox interview that he was untroubled by the criticism and thought Obama did a "nice job" in his comedy routine.
But he defended at length his views on foreign policy, which he outlined in a speech last week in Washington that drew criticism for sometimes contradictory views. Trump said he would move quickly to destroy Islamic State's militancy, but would resist interventionist policies in order to focus on nation-building at home.
Trump said "every move we made in the Middle East was wrong" over the past 15 years, with lives and money wasted. He said he would resist such policies.
Asked whether the United States should return to working with "strongmen" leaders like the late Iraqi President Saddam Hussein, Trump said: "Isn't it too bad that we knocked him out in the first place?"
(Additional reporting by David Lawder; Editing by Howard Goller)