Washington (CNN) On the eve the next 2016 contests, each of the remaining presidential candidates appeared Monday night on CNN to take on issues ranging from foreign policy to their own political futures.

Hillary Clinton launched her presidential bid on April 12 through a video message on social media. The former first lady, senator and secretary of state is considered the front-runner among possible Democratic candidates."Everyday Americans need a champion, and I want to be that champion -- so you can do more than just get by -- you can get ahead. And stay ahead," she said in her announcement video. "Because when families are strong, America is strong. So I'm hitting the road to earn your vote, because it's your time. And I hope you'll join me on this journey."

Ohio Gov. John Kasich joined the Republican field July 21 as he formally announced his White House bid. "I am here to ask you for your prayers, for your support ... because I have decided to run for president of the United States," Kasich told his kickoff rally at the Ohio State University.

Ohio Gov. John Kasich joined the Republican field July 21 as he formally announced his White House bid. "I am here to ask you for your prayers, for your support ... because I have decided to run for president of the United States," Kasich told his kickoff rally at the Ohio State University.

Sen. Ted Cruz of Texas has made a name for himself in the Senate, solidifying his brand as a conservative firebrand willing to take on the GOP's establishment. He announced he was seeking the Republican presidential nomination in a speech on March 23."These are all of our stories," Cruz told the audience at Liberty University in Virginia. "These are who we are as Americans. And yet for so many Americans, the promise of America seems more and more distant."

Businessman Donald Trump announced June 16 at his Trump Tower in New York City that he is seeking the Republican presidential nomination. This ends more than two decades of flirting with the idea of running for the White House."So, ladies and gentlemen, I am officially running for president of the United States, and we are going to make our country great again," Trump told the crowd at his announcement.

The CNN interviews also came on the same day that President Barack Obama held a historic news conference with Cuban leader Raul Castro , infusing the discussions with a lot of foreign policy talk.

Here's a look at the highlights from the interviews:

Donald Trump

Donald Trump said the U.S. should rethink its involvement in NATO because the defense alliance costs too much money.

In remarks to CNN's Wolf Blitzer, Trump said the U.S. pays a disproportionate amount to NATO to ensure the security of allies.

"Frankly, they have to put up more money," he said. "We are paying disproportionately. It's too much, and frankly it's a different world than it was when we originally conceived of the idea."

For instance, Trump said Washington was "taking care" of Ukraine and that other European nations were not doing enough to support the Kiev government that has been locked in a long showdown with Moscow.

But Ukraine is not a member of NATO, and Washington is not providing arms to the government as it is fighting pro-Moscow rebels, though has provided nonlethal aid and has helped support international bailouts of the Ukrainian economy.

Later in the interview, Trump qualified his remarks saying that the U.S. should not "decrease its role" in NATO but should decrease its spending. Still, the Republican presidential front-runner's NATO comments could spur anxiety among the Western foreign policy establishment.

"We need steady hands. Not a president who says he is neutral on Monday, pro-Israel on Tuesday and who knows what on Wednesday because everything is negotiable," Clinton said in a clear shot at the Republican front-runner.

But in the CNN interview, Trump said Clinton lacks the strength to be president and dismissed her claim that he was too volatile to be commander in chief.

JUST WATCHED Trump: Clinton doesn't have the stamina to be President Replay More Videos ... MUST WATCH Trump: Clinton doesn't have the stamina to be President 00:52

"Hillary Clinton does not have the stamina ... does not have the strength to be president," Trump told Blitzer.

Trump also dismissed Clinton's critique about his potential qualifications to serve as president.

"I have the steadiest hands. Look at those hands," Trump said. "Far steadier than hers," he said, accusing Clinton of simply reading speeches scripted by her aides off a teleprompter.

Trump also said that if elected president, he would require the removal of the U.S. embassy to Israel from Tel Aviv to Jerusalem in a reversal of long-standing American policy.

"It's a process but fairly quickly," Trump said, when asked how quickly he could make such a move happen.

He broke with many others in the GOP foreign policy establishment by saying he would continue the President's policy of normalizing relations with the former U.S. communist foe.

"Probably so," Trump said.

"But I want much better deals than we are making," Trump said, and said at the "right time" he would be willing to open one of his signature luxury hotels in Havana. He said that Castro had also delivered "a very, very big slight" to Obama by not meeting him at the airport when Air Force One touched down in Havana on Sunday.

The Republican front-runner also warned the party against depriving him of the GOP nomination if he falls marginally short of the 1,237 delegates needed to formally clinch the party's presidential election nod.

"If it was at 1190, so I am a little bit off .... I think it is going to be very hard for them to do," Trump said, pointing out he had several million more votes than any other candidate in the Republican primary process. He added that it was "a little unfair" that he had been forced to compete against so many Republican candidates in a manner that made it tougher for anyone to reach that magic number.

"I had many, many people that I am competing with, so you know when you talk about the majority plus one it is a very unfair situation."

Hillary Clinton

"He has been engaging in bigotry and bluster and bullying, and I think when it comes to understanding what he would do as president, there are serious questions that have been raised, and this campaign should he be the nominee will have to address them," Clinton told CNN's Anderson Cooper.

The former secretary of state accused Trump of inciting violence and urging supporters to go after protesters in a way that she said "raises very serious questions." Asked whether Trump would behave differently as president, Clinton answered "Who knows?"

Turning to her primary battle against Sanders, Clinton said that she did not "buy" polls that show the Vermont senator is a stronger Democratic general election candidate.

"Any horse race poll this far out is meaningless," Clinton said.

JUST WATCHED Clinton on Sanders: We've run a campaign on issues Replay More Videos ... MUST WATCH Clinton on Sanders: We've run a campaign on issues 00:45

She also argued that she was better at performing in governing jobs than running for office, in a fresh admission that her campaign skills are sometimes lacking.

"I think that the kind of results that I get when I am actually holding a position speak to that," she said.

She called on the Senate to quit "partisan posturing" and to hold hearings on Obama's nominee to the Supreme Court, Merrick Garland . But she would not say whether she would ask Obama to withdraw the pick if she becomes the Democratic nominee and had the chance as president of selecting a more progressive potential justice than Garland, who is seen by many liberals as a moderate.

"We have one president at a time; he has made his nomination," Clinton said.

Unlike the Republicans questioned by CNN, Clinton defended Obama's Iran nuclear deal , saying it was "on balance" the right step to take but recalled a speech last year in which she said the "slightest infraction" by Iran must have consequences. But she also hinted that she would seek a less contentious relationship with Israel than has been the case in the Obama administration.

"I think my firm commitment to Israel's security puts me on a very strong foundation to deal with whatever the questions might be in the relationship," she said.

Clinton joked that she and Israeli Prime Minister Benjamin Netanyahu "engage in vigorous discussion" when asked about reports she and the Israeli leader had yelled at each other in the past. But she also said that moving the U.S. Embassy to Jerusalem would be an inflammatory act unless it took place as part of a two-state solution between Israel and the Palestinians and would "light a fire" in an already unstable region.

Ted Cruz

Ted Cruz took swipes at Trump and Obama over their foreign policy.

He blasted the Obama administration for not living up to an agreement with Ukraine to secure its territorial integrity made at the end of the Cold War when Kiev gave up its Soviet-era nuclear weapons.

Cruz also slammed Obama's trip to Cuba, saying the President was in the company of celebrities who have glamorized the Castro brothers.

"As Barack Obama is sitting there sipping mojitos with brutal Communist dictators , he can't be bothered to meet the dissidents, he can't be bothered to visit with the Ladies in White, he can't be bothered to hear the screams of oppression," Cruz said.

Cruz, who is of Cuban descent, said what Obama was doing in Cuba was similar to what he was doing in Iran -- giving "billions of dollars" to enemies of America.

He then attacked Trump, accusing him of possessing a dangerous lack of knowledge about the world, after Trump said the U.S. should rethink its involvement in NATO.

"Everything I just said, I bet you dollars to doughnuts Donald Trump has no idea about any of that."

"It has been Russia's objective, it has been Putin's objective, for decades to break NATO. What Donald Trump is saying that he would unilaterally surrender to Russia and Putin, give Putin a massive foreign policy victory by breaking NATO and abandoning Europe."

The interview became contentious when the conversation turned to the controversial foreign policy views of Cruz adviser Frank Gaffney. CNN's Wolf Blitzer presented Cruz with a series of quotes from Gaffney, in which his adviser described Obama as a Muslim, said the Muslim Brotherhood had infiltrated the U.S. government and linked former Iraqi leader Saddam Hussein to the 1993 attack on the World Trade Center in New York and the Oklahoma City bombing in 1995.

JUST WATCHED Ted Cruz asked about his controversial adviser Replay More Videos ... MUST WATCH Ted Cruz asked about his controversial adviser 01:40

Cruz said Gaffney, a former defense official in the Reagan administration, was attacked by the media because he speaks about against Islamic extremism.

"I am not going to play the gotcha game of every quote every adviser may have given 20 years ago. I am actually interested in talking about the problems in this country, this is silliness."

Cruz also mocked Trump's knowledge of the Middle East following the billionaire's speech to AIPAC earlier Monday.

"His speech was actually an improvement. He clearly hired someone to write that speech for him," Cruz told Blitzer.

"One of the challenges with foreign policy that Donald's knowledge of the world is very, very limited," Cruz said.

Cruz did not find the idea of serving as the vice presidential nominee on a Trump presidential ticket attractive.

"I have no interest whatsoever in this," Cruz said. "If Donald Trump is the nominee it is a disaster. Donald may be the only candidate on the face of the Earth that Hillary Clinton can beat in a general election."

Bernie Sanders

Bernie Sanders opened his appearance by satellite from Salt Lake City, Utah, by explaining that he didn't snub AIPAC by being the only current White House hopeful not to address the group Monday, saying it was merely a question of scheduling.

He called for the United States to work with both sides in the Israeli-Palestinian conflict. He said Israel should have the right to defend itself but warned conditions in the Palestinian-ruled Gaza Strip need to be mitigated, and that people are contending with high unemployment and "horrific" poverty there.

Still, Sanders said he was "not happy ... with some of the behavior" of Prime Minister Benjamin Netanyahu, citing the Israeli leader's decision to accept an invitation to address the U.S. Congress about the Iran nuclear deal without notifying the White House.

Sanders backed Obama's Cuba diplomacy and hinted that it would be proper for Cuban leader Raul Castro to visit the White House.

"Last I heard, we have invited the leaders of Saudi Arabia, we have invited the leaders of China, we have invited the leaders of a whole lot of authoritarian countries to come to the United States," Sanders said. "I think Cuba should be treated similarly."

He also argued that he has better foreign policy judgment than Hillary Clinton, despite her having served as secretary of state.

JUST WATCHED Sen. Bernie Sanders: We could learn a lot from Cuba Replay More Videos ... MUST WATCH Sen. Bernie Sanders: We could learn a lot from Cuba 02:27

Regarding his battle with Clinton, Sanders rejected suggestions he should get out of the race because he trails the former secretary of state in the delegate count and argued that he was a stronger general election candidate than she is.

"I am not a quitter. We are going to fight this to the last vote," he said. We are going to give every American the chance to decide which candidate they want to be the Democratic nominee in November."

Sanders also hit out at Trump, saying the Republican front-runner "just says things off the top of his head."

"Time after time, he says things that are just not true."

John Kasich

Ohio Gov. John Kasich struck a more conventional foreign policy stance in his interview than Trump, especially on NATO.

"We clearly have to make sure we strengthen NATO, we have to make sure that (Russian President Vladimir) Putin understands we will arm the Ukrainians so they fight for freedom," Kasich told Anderson Cooper. "We need NATO. NATO is important; we all wish they would do more."

And he would not go as far as Trump on moving the U.S. embassy in Israel, though he took pains to describe his own speech to AIPAC on Monday as strongly pro-Israel.

JUST WATCHED Gov. John Kasich: I'd keep ISIS out of Libya Replay More Videos ... MUST WATCH Gov. John Kasich: I'd keep ISIS out of Libya 01:47

"It's easy to make a lot of statements, but when you have a lot of experience in this matter which I have ... you learn to choose your words carefully," Kasich said, adding that Trump was "dead wrong" on NATO -- though he declined to make a judgment -- on the GOP front-runner's personal qualities.

The Ohio governor also turned his fire on Clinton and her tenure as secretary of state, saying she had made a "terrible" mistake in intervening in Libya against longtime strongman Moammar Gadhafi.

"We should have let Gadhafi stay there," he said, saying that the Libyan leader's ouster had led to a "Wild West" situation in Libya exploited by terrorists.

Kasich ruled out any deal with Ted Cruz or Trump that would involve him taking a spot on their presidential tickets.

"First of all, there is zero chance that I would be vice president with either of them," Kasich said. "Below zero actually."