Jeb Bush Former Florida governor
Age on Election Day: 63
Religion: Catholic
Base: Moderates
Résumé: Former Florida governor and secretary of state. Former co-chair of the Barbara Bush Foundation for Family Literacy.
Education: B.A. University of Texas at Austin.
Family: Married to Columba Bush (1974), with three adult children. Noelle Bush has made news with her struggle with drug addiction, and related arrests. George P. Bush was elected Texas land commissioner in 2014. Jeb's father George H.W. Bush was the 41st President of the United States, and his brother George W. Bush was number 43.
Claim to fame: Jeb was an immensely popular governor with strong economic and jobs credentials. He is also one of just two GOP candidates who is fluent in Spanish.
Achilles heel: Bush has angered conservatives with his permissive positions on illegal immigration (saying some border-crossing is 'an act of love) and common-core education standards. His last name could also be a liability with voters who fear establishing a family dynasty in the White House.
Chris Christie New Jersey governor
Age on Election Day: 54
Religion: Catholic
Base: Establishment-minded conservatives
Résumé: Governor of New Jersey. Former U.S. Attorney for the District of New Jersey. Former Morris County freeholder and lobbyist.
Governor of New Jersey. Former U.S. Attorney for the District of New Jersey. Former Morris County freeholder. Former statehouse lobbyist.
Education: B.A. University of Delaware, Newark, J.D. Seton Hall University.
Family: Married to Mary Pat Foster (1986) with four children.
Claim to fame: Pugnacious and unapologetic, Christie once told a heckler to 'sit down and shut up' and brings a brash style to everything he does. That includes the post-9/11 criminal prosecutions of terror suspects that made his reputation as a hard-charger.
Achilles heel: Christie is often accused of embracing an ego-driven and needlessly abrasive style. His administration continues to operate under a 'Bridgegate' cloud: At least two aides have been indicted in an alleged scheme to shut down lanes leading to the George Washington Bridge as political retribution for a mayor who refused to endorse the governor's re-election.
Carly Fiorina Former tech CEO
Age on Election Day: 62
Religion: Episcopalian
Base: Conservatives
Résumé: Former CEO of Hewett-Packard. Former group president of Lucent Technologies. Former U.S. Senate candidate in California.
Education: B.A. Stanford University. UCLA School of Law (did not finish). M.B.A. University of Maryland. M.Sci. Massachusetts Institute of Technology.
Family: Married to Frank Fiorina (1985), with one adult step-daughter and another who is deceased. She has two step-grandchildren. Divorced from Todd Bartlem (1977-1984).
Claim to fame: Fiorina was the first woman to lead a Fortune 20 company, something that could provide ammunition against the Democratic Party's drive to make Hillary Clinton the first female president. She is also the only woman in the 2016 GOP field, making her the one Republican who can't be accused of sexism.
Achilles heel: Fiorina's unceremonious firing by HP's board has led to questions about her management and leadership styles. And her only political experience has been a failed Senate bid in 2010 against Barbara Boxer.
Lindsey Graham South Carolina senator
Age on Election Day: 61
Religion: Southern Baptist
Base: Otherwise moderate war hawks
Résumé: U.S. senator. Retired Air Force Reserves colonel. Former congressman. Former South Carolina state representative.
Education: B.A. University of South Carolina. J.D. University of South Carolina Law School.
Family: Never married. Raised his sister Darline after their parents died while he was a college student and she was 13.
Claim to fame: Graham is a hawk's hawk, arguing consistently for greater intervention in the Middle East, once arguing in favor of pre-emptive military strikes against Iran. His influence was credited for pushing President George W. Bush to institute the 2007 military 'surge' in Iraq.
Achilles heel: Some of his critics have taken to call him 'Grahamnesty,' citing his participating in a 2013 'gang of eight' strategy to approve an Obama-favored immigration bill. He has also aroused the ire of conservative Republicans by supporting global warming legislation and voting for some of the president's judicial nominees.
Bobby Jindal Louisiana governor
Age on Election Day: 45
Religion: Catholic
Base: Social conservatives
Résumé: Governor of Louisiana. Former congressman. Former Assistant Secretary of Health and Human Services for Planning and Evaluation. Former Secretary of the Louisiana Department of Health and Hospitals.
Education: B. Sci. Brown University. M.Litt. New College at Oxford University
Family: Married to Supriya Jolly (1997), with three children, each of whom has an Indian first name and an American middle name. Bobby Jindal's given name is Piyush.
Claim to fame: Jindal's main source of national attention has been his strident opposition to federal-level 'Common Core' education standards, which included a federal lawsuit that a judge dismissed in late March. He is also outspoken on the religious-freedom issues involved in mainstreaming gay marriage into the lives of American Christians.
Achilles heel: During his first term as governor, Jindal signed a science education law that requires schools to present alternatives to the theory of evolution, including religious creationism. His staunch defense of businesses that want to steer clear of providing services to same-sex couples at their weddings will win points among evangelicals but alienate others.
George Pataki Former New York governor
Age on Election Day: 71
Religion: Catholic
Base: Centrists
Résumé: Former governor of New York. Former New York state senator and state assemblyman. Former mayor of Peekskill, NY.
Education: B.A. Yale University. J.D. Columbia Law School.
Family: Married to Libby Rowland (1973), with four adult children.
Claim to fame: Pataki was just the third Republican governor in New York's history, winning an improbable victory over three-term incumbent Mario Cuomo in 1994. He was known for being a rare tax-cutter in Albany and was also the sitting governor when the 9/11 terror attacks rocked New York CIty in 2001.
Achilles heel: While Pataki's liberal-leaning social agenda plays well in the Empire State, it won't win him any fans among the GOP's conservative base. He supports abortion rights and gay rights, and has advocated strongly in favor of government intervention to stop global warming, which right-wingers believe is overblown as a global threat.
Marco Rubio Florida senator
Age on Election Day: 45
Religion: Catholic
Base: Conservatives
Résumé: US senator, former speaker of the Florida House of Representatives, former city commissioner of West Miami
Education: B.A. University of Florida. J.D. University of Miami School of Law.
Family: Married to Jeanette Dousdebes (1998), with two sons and two daughters. Jeanette is a former Miami Dolphins cheerleader who posed for the squad’s first swimsuit calendar.
Claim to fame: Rubio's personal story as the son of Cuban emigres is a powerful narrative, and helped him win his Senate seat in 2010 against a well-funded governor whom he initially trailed by 20 points.
Achilles heel: Rubio was part of a bipartisan 'gang of eight' senators who crafted an Obama-approved immigration reform bill in 2013 which never became law – a move that angered conservative Republicans. And he was criticized in 2011 for publicly telling a version of his parents' flight from Cuba that turned out to appear embellished.
Donald Trump Real estate developer
Age on Election Day: 70
Religion: Presbyterian
Base: Conservatives
Résumé: Chairman of The Trump Organization. Fixture on the Forbes 400 list of the world's richest people. Star of 'Celebrity Apprentice.'
Education: B.Sci. Wharton School of the University of Pennsylvania
Family: Married to Melania Trump (2005). Divorced from Ivana Zelníčková (1977-92) and Marla Maples(1993–99). Five grown children. Trump's father Fred Trump amassed a $400 million fortune developing real estate.
Claim to fame: Trump's niche in the 2016 campaign stems from his celebrity as a reality-show host and his enormous wealth – more than $10 billion, according to Trump. Because he can self-fund an entire presidential campaign, he is seen as less beholden to donors than other candidates. He has grabbed the attention of reporters and commentators by unapologetically staking out controversial positions and refusing to budge in the face of criticism.
Achilles heel: Trump is a political neophyte who has toyed with running for president and for governor of New York, but shied away from taking the plunge until now. His billions also have the potential to alienate large swaths of the electorate. And his Republican rivals have labeled him an ego-driven celeb and an electoral sideshow because of his all-over-the-map policy history – much of which agrees with today's Democrats – and his past enthusiasm for anti-Obama 'birtherism.'