Jeb Bush Former Florida governor
Age: 62
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: 52
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 CEO
Age: 60
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: 59
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: 44
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: 69
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.
Rick Perry Former Texas governor
Age: 65
Religion: Christian (nondenominational)
Base: Conservatives
Résumé: Former Texas governor, lieutenant governor, agriculture commissioner and state representative.
Education: B.Sci. Texas A&M University
Family: Married to Anita Thigpen (1982) with two adult children. His father was a former Democratic county commissioner in Texas.
Claim to fame: Perry boasts that while he was governor between the end of 2007 and the end of 2014, the Texas economy created 1.4 million new jobs while the rest of the U.S. lost close to 400,000. A Perry-led Texas also had the nation's highest high school graduation rate among Hispanics and African-Americans.
Achilles heel: Perry has a tough hill to climb after his 2012 presidential campaign spectacularly imploded with a single word 'Oops' after he couldn't remember one of his own talking points during a nationally televised debate. He also faces an indictment for alleged abuse of power in a case that Republicans contend is politically motivated and meritless.
Rick Santorum Former Penn. senator
Age: 57
Religion: Catholic
Base: Evangelicals
Résumé: Former US senator and former member of the House of Representatives from Pennsylvania. Former lobbyist who represented World Wrestling Entertainment.
Education: B.A. Penn State University. M.B.A. University of Pittsburgh. J.D. Penn State University Dickinson School of Law.
Family: Married to Karen Santorum (1990), with seven living children. One baby was stillborn in 1996. Another, named Isabella, is a special needs child with a genetic disorder.
Claim to fame: Santorum won the 2012 Republican Iowa Caucuses by a nose. He won by visiting all of Iowa's 99 states in a pickup truck belonging to his state campaign director, a consultant who now worls for Donald Trump.
Achilles heel: As a young lobbyist, Santorum persuaded the federal government to exempt pro wrestling from regulations governing the use of anabolic steroids. And the stridently conservative politician has attracted strong opposition from gay rights groups. One gay columnist held a contest to redefine his name, buying the 'santorum.com' domain to advertise the winning entry which is too vulgar to print.
Scott Walker Wisconsin governor
Age: 47
Religion: Christian (nondenominational)
Base: Conservative activists
Résumé: Governor of Wisconsin. Former Milwaukee County Executive. Former member of the Wisconsin State Assembly.
Education: Marquette University (did not finish)
Family: Married to Tonette Tarantino (1993), with two children. One of Mrs. Walker's cousins is openly lesbian and was married in 2014, with the Walkers attending the reception.
Claim to fame: Walker built his national fame on the twin planks of turning his state's past budget shortfalls into surpluses and beating back a labor-union-led drive to force him out of office through a recall election. Both results have broad appeal in the GOP.
Achilles heel: Wisconsin has suffered from a shaky economy during Walker's tenure, which makes him look weak compared with other governors who presided over more robust job-creation numbers. He promised to create 250,000 private sector jobs but delivered less than 60 per cent of them. Also, he led an effort in the state legislature to enact $800 million in tax cuts putting the Badger State back on the road to government deficits.