Rand Paul didn't graduate from college (and 9 other facts you should know about the 2016 candidate)

By ISABELLE CHAPMAN

Kentucky Senator Rand Paul became the second Republican to formally enter the race for the White House Tuesday morning, saying he hopes to return the United States to the "principles of liberty and limited government."

The Pennsylvania-born ophthalmologist rode the tea party wave into Washington in 2010 when Kentucky voters elected him to serve as their U.S. senator. He comes from a political family; his father Ron Paul is a former Texas congressman who served for many years and ran for president in 1988, 2008 and 2012.

Much like his father, the 52-year-old 2016 hopeful doesn't toe the Republican party line on all issues. He advocates government with limited power and smaller federal budgets, but believes in restricting defense spending too -- a third rail many hawkish Republicans avoid. He's also supported decriminalization of marijuana and is a vocal critic of President Obama's drone policy.

He conducted a filibuster that lasted nearly 13 hours in opposition of the nomination of John Brennan as director of the CIA, who oversaw Obama's drone program, in 2013. Paul covered an array of topics during his time at the podium -- including wondering if the United States would have dropped a drone on Jane Fonda when she traveled to Vietnam during the Vietnam War.

While he is a physician, Paul has one thing in common with majority of "average joes" in America: He never got his bachelor's degree. He left Baylor University to attend Duke University School of Medicine without having finished his undergraduate course work. At the time, Duke did not require an undergraduate degree if a student's test scores were adequate.

While about two-thirds of Americans don't have an undergraduate degree, according to the latest Census data, it's rather unusual for a president in modern history. Harry Truman was the last man in the Oval Office who hadn't earned a bachelor's degree.

However, many pre-20th century presidents led the country without one, including Abraham Lincoln, Martin Van Buren, Zachary Taylor, Grover Cleveland, among others. If Wisconsin Gov. Scott Walker decides to run in 2016, Paul won't be the only candidate with this distinction either -- Walker attended Marquette University but never graduated.

Click through the gallery above for other details you might not know about the presidential hopeful.