SIMI VALLEY, Calif. - Republican front-runner Donald Trump traded jabs with former Florida Governor Jeb Bush, former business executive Carly Fiorina and other presidential rivals in a contentious three-hour-long debate on Wednesday marked by frequent bickering and personal attacks.In the second debate of the 2016 Republican White House race, the candidates battled over Iraq and condemned President Barack Obama's nuclear deal with Iran among foreign policy issues.With Trump shooting to a big lead in opinion polls in the Republican presidential race, the other 10 candidates on the crowded debate stage struggled at times for attention barely four months before the first nominating contest for the November 2016 election.But unlike last month's first debate, when most of the contenders shied away from directly challenging Trump, several candidates engaged in sometimes fierce personal exchanges with the real estate mogul and former reality-TV star.Among the candidates,Ted Cruz, a US senator from Texas, said the nuclear deal with Iran should be ripped up, but Kentucky Senator Rand Paul said it should be enforced because Congress had not been able to stop it.Cruz pointed to the threat of a nulcear Iran as the main threat to America's national security, saying the deal back by the Obama administration will provide Iran with $100 billion, "making the Obama administration the world's leading financier of radical Islamic terrorism."Former Arkansas Governor Mike Hukabee also came out staunchly against the nuclear deal with Iran, saying the current administration treats it like the "Magna Carta," while "Iranians treat it like it's toilet paper."He stressed that the next US president, whomever it may be, will "destroy" the deal and take a tough stance on Iran.The deal "threatens Israel immediately, this threatens the entire Middle East, but it threatens the United States of America," said Hukabee. "This is a government for 36 years has killed Americans, they kidnapped Americans, they have maimed Americans. They have sponsored terrorist groups, Hamas and Hezbollah, and they threaten the very essence of Western civilization." Newcomer Fiorina state that if elected, on her first day in the Oval Office she would first call her "good friend" Prime Minister Benjamin Netanyahu to reassure him of Washington's support for Israel. "The second, to the supreme leader [of Iran, Ali Khamenei], to tell him that unless and until he opens every military and every nuclear facility to real anytime, anywhere inspections by our people, not his, we, the United States of America, will make it as difficult as possible and move money around the global financial system," said the former businesswoman.Meanwhile, former Florida governor Jeb Bush said tearing up the agreement with Iran would not serve as a strategy.He said instead a strategy would consist of devising a plan to confront Iran, including providing Israel with the most advanced arms that would reverberate with a message to the Islamic Republic. Florida Senator Marco Rubio also chimed in on the Iran issue, saying it allows the Tehran regime with a"radical Shia cleric with an apocalyptic vision of the future" to achieve nuclear weapons capabilities and long-range rockets that can strike the US."We have a president that is more respectful to the ayatollah in Iran than he is to the prime minister of Israel," he charged.