From 'Middle-Class Joe' to millionaire: Joe Biden is worth an estimated $9 million. Here's a look at the lifestyle, finances, and real-estate portfolio of one of the leading Democratic presidential candidates.

Former Vice President Joe Biden is one of the leading 2020 Democratic presidential candidates.

Biden was ranked No. 1 in Insider's recent "Power Ranking" of which candidate has the best chance of becoming the 2020 Democratic presidential nominee.

The 77-year-old former senator has the edge in the polls.

Based on a recurring series of national surveys conducted by Insider, many people who would be satisfied with Biden as the nominee are unconvinced about almost all of the other candidates in the race.

Biden recovered the lead over Senator Elizabeth Warren in RealClearPolitics' polling average after coming in first place in the Quinnipiac poll of New Hampshire. The last-minute entrances of moderates Michael Bloomberg and Deval Patrick did not seem to impact Biden's lead.

While many Americans perceive Biden as likable, many also take issue with his candidacy.

A June INSIDER poll found Biden was ranked by respondents as more likable or personable candidate than his opponents 78% of the time, but that doesn't mean he isn't contending with significant criticism regarding policy and more.

In the spring, Biden addressed accusations that he made several woman feel uncomfortable due to inappropriate touching.

In the summer, Biden fondly recalled working with two segregationist senators, later apologizing for it.

Most recently, analysts have expressed concerned with Biden's age — should he win the nomination, and then the presidency, the possibility of a second term would be questionable. He would be 86 in 2028.

The 2020 Democratic primary marks the third presidential race Biden has entered — but the first as a millionaire.

Biden's political career took off in 1972, when he was elected to the US Senate. He unseated Republican J. Caleb Boggs to become the fifth-youngest senator in history. He then continued to serve as a Delaware senator for over 30 years.

Biden has famously touted himself as the poorest member of the Senate and referred to himself as "Middle-Class Joe."

In 2008, he was the running mate for Democratic Presidential Candidate Barack Obama. From 2009 to 2017, he served as Vice President of the United States with Obama as president.

Prior to the 2020 election cycle, Biden had run for president twice: first in 1988, and again in 2008. The first run ended in a plagiarism scandal; the second time around, he withdrew from the race after the Iowa caucus.

Forbes estimates that as of July 2019, Biden and his wife, Jill, are collectively worth $9 million. Some of that comes from his senatorial salary.

Since 1998, the first year Biden released his tax returns, the majority of the Bidens' income was attributed to his Senate salary and her community college professor's salary, according to Forbes.

Biden's salary in 2009, his last year in the Senate, was $169,000. The vice presidency came with a 30% raise; he earned an average of $225,000 per year and served as vice president from 2009 to 2017. Forbes also reported that the pair received roughly half a million dollars in pensions and social security benefits over the course of those eight years.

But the majority of the Bidens' wealth was built after he left office.

The couple has made more than $15 million from book royalties.

Joe Biden has written two books over the past 11 years:

• "Promises to Keep," released in 2008 right after his presidential run announcement, was Biden's first memoir. It did not sell well initially, but the New York Times reported book sales picked up after Biden was announced as Obama's running mate. In 2013, the United Press International reported the book was ultimately not lucrative — Biden's financial disclosures showed book royalties "close to zero."
• "Promise me, Dad," released in 2017, is an account of Beau Biden's death from cancer. It topped the U.S. bestsellers list briefly after its release and has sold over 300,000 copies.

And then there's the money Biden has made off of promoting his 2017 bestseller, "Promise Me, Dad." According to Biden's recent financial disclosures, he was paid anywhere from $8,000 to $90,000 per single book-tour stop.

The book tour resulted in $1.8 million, according to Forbes. Public speaking engagements also contributed $2.4 million to the couple's net worth — and Jill's speaking fees tacked $700,000 on to that. CNBC reported that Biden took in as much as $190,000 in March 2018 for one lecture at Drew University in New Jersey.

In total, the couple earned more than $15 million, according to tax filings, from book royalties and speaking events and professor of practice fees provided by the University of Pennsylvania starting in 2017.

The Bidens have endured a number of personal tragedies.

A month after Biden's election to the US Senate in 1972, his wife Neilia and 1-year-old daughter Naomi were killed in a car accident. The couple's two sons, Beau and Robert, were also in the car, but survived.

Biden went on to marry Jill Jacobs in 1977. The pair had a daughter, Ashley, in 1981.

Biden underwent brain surgery for two potentially deadly aneurysms in 1988 but was back to work within seven months. During his second term as vice president, 27 years later, his 46-year-old son Beau died of brain cancer.

The death of his 46-year-old son Beau played a prominent role in Biden's decision to sit out the 2016 presidential election.

Although many believed Biden would have fared better than Hillary Clinton, Biden opted to steer clear of the 2016 presidential race to grieve. His grief was later widely addressed by the aforementioned memoir, "Promise Me, Dad."

In January, Politico's Michael Kruse described empathy stemming from personal tragedy as the quality that makes Biden electable: "There is no person in American politics today whose life has been so shaped by loss and grief," he wrote, noting that Biden's personal history gives him the unique opportunity to immediately connect with those who have experienced loss themselves.

The family's primary residence is in Delaware.

The Washington Post reported that the Bidens' primary residence is a home the family built over 20 years ago in Wilmington, Delaware. The lakeside property is said to be nearly 7,000 square feet.

The family also purchased a $2.7 million Delaware beach home in 2017.

The waterfront property is 4,800 square feet.

The Bidens also recently rented a lavish mansion in McLean, Virginia, according to the Washington Post.

They started renting it in 2017 after vacating the vice presidency. The rental price for the sprawling 12,000-square-foot residence with marble finishes, a gym, sauna, and enough parking for 20 cars was referred to as "substantial" by Biden's campaign in June 2019.

The Washington Post determined that the monthly rent for the home hovered around $20,000, according to Zillow.

The family's recent real-estate activity can be attributed to lucrative book royalties and speaking engagements.

Biden also holds a position at the University of Pennsylvania that carries an annual salary of $400,000 as a professor and the namesake of The Biden Center for Diplomacy and Global Engagement.

All in all, the couple reported earning $11 million immediately after leaving the White House in 2017 and $4.5 million in 2018.

Even with his multimillionaire status, Biden is far from the richest Democratic presidential candidate.

South Bend, Indiana, Mayor Pete Buttigieg has an estimated net worth of about $100,000. Former tech CEO Andrew Yang is worth about $1 million.

Bernie Sanders and his wife, Jane, are worth an estimated $2.5 million, according to Forbes. In both 2016 and 2017, the Vermont senator earned more than $1 million, largely from book royalties, financial-disclosure documents show — an income strategy similar to Biden and Senator Elizabeth Warren, who, with her husband, is worth an estimated $12 million. In addition to book royalties, Warren's wealth is largely tied to retirement accounts and real estate.

Beyond Warren stands Colorado senator Michael Bennet, worth an estimated $15 million, and former Maryland representative John Delaney, worth an estimated $232 million.

The richest of the Democrat hopefuls (by a wide margin) are former hedge-fund manager Tom Steyer, who's worth an estimated $1.6 billion and Michael Bloomberg, who's worth an estimated $56 billion, both according to Forbes.