Story updated on April 8, 2015

US Kentucky senator Rand Paul, 52, has launched his campaign for the Republican presidential nomination race.

His declaration on Tuesday - the second one from a Republican - is expected to be followed by a slew of others. Florida Senator Marco Rubio is due to announce his candidacy next week. Latest polls show Dr Paul, an ophthalmologist, lagging behind establishment-backed party contenders like Wisconsin governor Scott Walker and former Florida governor Jeb Bush.

Here are 10 fast facts about Dr Paul:

1. Growing up

Dr Paul, whose full name is Randal Howard Paul, was born on Jan 7, 1963, in Lake Jackson, Texas. He is the middle of five children born to Ron and Carol Paul. His father was elected to the House of Representatives in 1976 and ran for US president in 2008. He is married to Kelley Ashby Paul and have three sons.

2. Career

He is an opthamologist, specialising in cataract and glaucoma surgeries, lasik procedures and corneal transplants. In 1995, he founded the Southern Kentucky Lions Eye Clinic, an organisation that provides eye tests and surgery to needy families and individuals. He is a former president and member of the Lions Clubs International, which is dedicated to preserving eyesight by providing eyeglasses and surgery to the less fortunate around the world.

3. Elected to the Senate in 2010

Dr Paul was elected to the Senate in 2010 in Kentucky on the momentum of his father's very libertarian campaign. Few believe that Dr Paul, who had never been elected to anything, could have won a Senate seat without such a famous last name.

4. What he needs to be a presidential nominee

Though heavily influenced by his father's socially conservative, free-market, non-interventionist school of libertarianism, Dr Paul is different in one significant way: He needs moderate and establishment Republicans in his camp if he wants to be the presidential nominee. And the more purist libertarians who supported his father have never fully embraced him.

5. Recent comments on gay marriage

His recent comments on gay marriage - "personally offended" and "moral crisis" - have stirred up a libertarian backlash. Unlike him, most libertarians support abortion rights. But voters for whom abortion and gay marriage are deal-breakers aren't likely to be voting in Republican primaries.

6. Foreign policy moves

Many libertarian activists have also objected to his foreign policy moves, including his endorsement of US airstrikes against the Islamic State in Iraq and Syria (ISIS), and his proposal for a US$190 billion (S$256 billion) increase in defence spending over the next two years that would be paid for by cutting foreign aid and other government programmes.

7. Iran

He has also been criticised for being weak on Iran and for showing apparent support for President Barack Obama's Iran policy, which polls show is deeply unpopular among Republican voters. Critics say he supports more negotiations with Iran while standing against more sanctions that would hold the Iranian regime accountable. That, they say, is not a conservative position but Mr Obama's position.

8. Campaign slogan

His campaign slogan is "Defeat the Washington machine. Unleash the American dream." The unwieldy slogan is meant to frame Dr Paul as a political outsider and is designed to evoke populist, anti-establishment themes that would work in both the primaries and the general election. Advisers say his top issues will include a flat tax, Internal Revenue Service reform, term limits, privacy and justice reform.

9. Good standing

Analysis from Republican insiders in the early nomination states suggests that he is already seen among the top tier of Republican presidential aspirants including former Florida governor Jeb Bush, Wisconsin governor Scott Walker and Florida senator Marco Rubio. He is especially well-placed to make a mark in New Hampshire, a state with strong libertarian tendencies where the rules permit voters outside the GOP to cast a ballot in the primary.

10. Announcement tour

The Kentucky Republican will kick off a five-day, five-state announcement tour starting in Kentucky and then to New Hampshire, South Carolina, Iowa and Nevada.

SOURCE: http://www.randpaul2016.com , WASHINGTON POST, POLITICO, NEWSWEEK, BLOOMBERG