Sen. Kamala Harris, left and Sen. Kirsten Gillibrand Andrew Lichtenstein | Corbis News | Getty Images

The first primary isn't until February, but there's no shortage of Democratic contenders hoping to take on President Donald Trump in 2020. Nearly two dozen candidates are seeking the Democratic nomination, from upstarts like Pete Buttigieg to lawmakers to seasoned veterans like Joe Biden. The field also contains an unprecedented number of women, including Kamala Harris and Elizabeth Warren. Here are the candidates and some of their main policy points:

Joe Biden

Vice President Joe Biden Getty Images

Age: 76 Announced bid: April 25 Who he is: Biden served as vice president in the Obama administration from 2009 to 2017. Before that, he represented Delaware in the Senate for 36 years, making him the state's longest-serving senator. This is the third time he's launched a presidential bid, having previously tried in the 1988 and 2008 cycles. Main issues: Before Biden announced his run, CNBC learned his team was drafting a proposal for infrastructure reform that could provide an alternative to Trump's sidelined $1 trillion plan. Biden has also called for a middle-class tax cut and has been vocal about women's rights. In 1994, Biden crafted the Violence Against Women Act, which protects victims of domestic and sexual assault and funds programs that aids survivors.

Cory Booker

Senator Cory Booker gestures during Day 1 of the Democratic National Convention at the Wells Fargo Center in Philadelphia, Pennsylvania, July 25, 2016. Robyn Beck | AFP | Getty Images

Age: 49 Announced bid: Feb. 1 Who he is: Booker is a Rhodes scholar who has been representing New Jersey in the Senate since 2013. Prior to his Senate election, Booker was the mayor of Newark for more than seven years. Before that, he served on the Newark City Council from 1998 to 2002. Main issues: Booker is looking to tackle criminal justice reform. Throughout his career, he has pushed to improve America's prison system and helped pass the First Step Act, which gives judges more discretion when sentencing some drug offenders. Booker wants to legalize marijuana at a federal level and is a co-sponsor of "Medicare for All," a push for universal health care introduced by Sen. Bernie Sanders.

Pete Buttigieg

Pete Buttigieg, the mayor of South Bend, Indiana, and 2020 presidential candidate, pauses during the South By Southwest (SXSW) conference in Austin, Texas, U.S., on Saturday, March 9, 2019. Callaghan O'Hare | Bloomberg | Getty Images

Age: 37 Announced bid: Jan. 23 Who he is: Buttigieg is serving his eighth and final year as the mayor of South Bend, Indiana, which was a population of about 102,000. He was elected at age 29, making him the youngest mayor of a city that size at the time. Buttigieg, a Rhodes scholar, was also in the Navy and is an Afghanistan War veteran. He is the first openly gay candidate to run for president. Main issues: Buttigieg has purposefully waited to unveil any specific policy plans, but his support for universal health care, combating climate change and taxing the wealthy has displayed his progressive views, though he's more moderate than other Democrats. Buttigieg says the U.S. should extend Medicare to anyone who wants it but does not believe that requires getting rid of private insurance. He also supports the "premise" of the Green New Deal and is in favor of increasing taxes on wealthy Americans.

Julián Castro

Mayor of San Antonio, Texas, Julian Castro speaks during the opening plenary session of Families USA's Health Action 2014 conference January 23, 2014 in Washington, DC. Getty Images

Age: 44 Announced bid: Jan. 12 Who he is: Before becoming the youngest member of President Barack Obama's Cabinet, Castro was mayor of San Antonio, Texas from 2009 to 2014. Castro was the U.S. secretary of Housing and Urban Development from 2014 to 2017. Main issues: The grandson of Mexican immigrants, Castro has been vocal against Trump's immigration policies. He suggested in an interview with CBS' "Face the Nation" that the U.S. use ankle monitors as an alternative to detentions and deportations, so immigrants could live freely in the country until their immigration trials. He also supports raising the minimum wage and enforcing the Affirmatively Furthering Fair Housing Rule, which requires cities receiving federal housing money to inspect any potential biases in housing opportunities.

John Delaney

Rep. John Delaney Katherine Frey | The Washington Post | Getty Images

Age: 55 Announced bid: July 28, 2017 Who he is: Delaney, a millionaire, was once the youngest CEO of a company traded on the New York Stock Exchange. After leading two companies, he was named an Ernst & Young Entrepreneur of the Year Award winner in 2004. Delaney then represented Maryland in the House from 2012 to 2017, when he announced his bid for president. Main issues: Delaney's campaign website says "hyper-partisanship" has broken our politics. To fix this, he proposed the Open Democracy Act to end gerrymandering and make Election Day a federal holiday. He also supports overturning Citizens United, which granted businesses, nonprofits and unions unlimited political spending power.

Tulsi Gabbard

U.S. Rep. Tulsi Gabbard (D-HI) speaks during a meet-and-greet at United Way of Southern Nevada on March 18, 2019 in Las Vegas, Nevada. Ethan Miller/Getty Images

Age: 38 Announced bid: Jan. 12 Who she is: Gabbard has been representing Hawaii in the House since 2013. She is the first Hindu member of Congress. A member of the National Guard, she completed a 12-month tour to Iraq as a field medical unit specialist in 2005. Before her deployment, Gabbard was the youngest person ever elected to the Hawaii Legislature at age 21. Main issues: Gabbard is a critic of interventionist wars in the Middle East and supports ending the war in Syria. Her campaign website suggests stopping the "illegal and counterproductive" attempt overthrow Syrian leader Bashar Assad. She also supports universal health care and wants to reform Wall Street by breaking up big banks and reinstating the Glass-Steagall Act, which limits the relationship between investment firms and commercial banks.

Kirsten Gillibrand

Sen. Kirsten Gillibrand (D-NY) Chip Somodevilla | Getty Images

Age: 52 Announced bid: Jan. 15 Who she is: Gillibrand has been a senator from New York since 2009, following a two-year term in the House. Before her tenure in Congress, she was an attorney in New York and special counsel to the U.S. secretary of Housing and Urban Development during the Clinton administration. Main issues: A staunch supporter of the #MeToo movement, Gillibrand has made women and family rights a priority. Her key policy is the FAMILY Act, which would mandate workers be given 12 weeks of paid family and medical leave to care for a new child, a sick family member or themselves. She's also a co-sponsor of "Medicare for All."

Kamala Harris

Sen. Kamala Harris Elijah Nouvelage | Reuters

Age: 54 Announced bid: Jan. 21 Who she is: Harris is representing California in her first Senate term after being elected in 2016. She is the second black woman to ever be elected to the Senate. Prior to assuming her seat, Harris was the attorney general of California. She was also district attorney of San Francisco from 2004 to 2011. She is also of Indian ancestry. Main issues: Harris' biggest priority is raising salaries for every teacher in the United States. She proposed a $315 billion investment that would boost teachers' pay by $13,500. She also is a co-sponsor of "Medicare for All" and wants to reform the criminal justice system by legalizing marijuana at the federal level and changing the cash bail system.

John Hickenlooper

Colorado Gov. John Hickenlooper. F. Carter Smith | Bloomberg | Getty Images

Age: 67 Announced bid: March 4 Who he is: Hickenlooper, who was mayor of Denver from 2004 to 2011, recently finished his second and final term as governor of Colorado. Prior to his political career, he was a geologist-turned-entrepreneur who opened 15 brew pubs and restaurants across the Midwest. Main issues: In a video that launched his campaign, Hickenlooper said he is looking to limit methane gas emissions and fight climate change. He also supports raising the federal minimum wage and enforcing gun safety restrictions. Though he is in favor of universal health care, he doesn't back "Medicare for All."

Jay Inslee

Governor Jay Inslee Olivia Michael | CNBC

Age: 68 Announced bid: March 1 Who he is: Inslee has been governor of Washington since 2013. In 2018, he served as chair of the Democratic Governors Association. He's also represented Washington twice in the House – from 1993 to 1995 and from 1999 to 2012. Main issues: The biggest issue Inslee is tackling is climate change. His campaign website says Inslee has "the proven experience" to turn Rep. Alexandria Ocasio-Cortez's proposed Green New Deal plan into action. He recommends powering the economy with clean energy, fighting for environmental justice and ending fossil fuel giveaways.

Amy Klobuchar

U.S. Sen. Amy Klobuchar (D-MN) addresses voters and answers questions while campaigning for the Democratic presidential nomination at the Pizza Ranch restaurant March 16, 2019 in Independence, Iowa. Chip Somodevilla/Getty Images

Age: 58 Announced bid: Feb. 10 Who she is: Klochubar has been representing Minnesota in the Senate since 2007. She is the state's first female senator. Before her political career, Klochubar was the prosecutor for Minnesota's most populous county, Hennepin. Main issues: The Minnesota Democrat wants to focus on affordable health care. Though Klobuchar isn't calling for a dramatic overhaul of the health system, she is pushing for lower drug prices and has backed the expansion of Medicare and Medicaid. She's also focused on online security. She wants to increase protections for online consumers by potentially regulating social media companies.

Wayne Messam

Miramar Mayor Wayne Messam. Brynn Anderson | AP Photo

Age: 44 Announced bid: March 28 Who he is: Messam is serving his second term as mayor of Miramar, Florida, which has a population of about 140,000. He is the first African American to be elected mayor of the city. Before his election, he served as a city commissioner from 2011 to 2015. He is also president of the National Black Caucus of Local Elected Officials and owns a construction company that manages climate-friendly projects. Main issues: Messam wants to increase gun safety and tackle high health costs, student loan debt and climate change. Messam's spokeswoman told CNBC in March that he would "absolutely" reenter the United States in the Paris Agreement, a multination pact that Trump abandoned and seeks to reduce greenhouse gas emissions around the world.

Seth Moulton

U.S. Representative Seth Moulton (D-MA). Michael Brochstein | LightRocket | Getty Images

Age: 40 Announced bid: April 22 Who he is: Moulton is in his second term representing Massachusetts in the House. The congressman also worked in the private sector in Texas to help build the country's first high-speed rail line. Moulton also served as a Marine from 2002 to 2008 and completed four tours in the Iraq War. Main issues: Moulton's campaign website lists national security as a main issue he wants to tackle. He wants to invest in autonomous, hypersonic and cyberweapons to replace "outdated, costly" systems. Moulton also wants to provide a public health care option that citizens have the option to sign up for and supports the Green New Deal to fight climate change.

Beto O'Rourke

Democratic 2020 presidential candidate Beto O'Rourke speaks during a campaign stop at The Beancounter Coffeehouse & Drinkery in Burlington, Iowa, U.S. March 14, 2019. Daniel Acker | Reuters

Age: 46 Announced bid: March 14 Who he is: O'Rourke is a former Texas congressman who was elected to the House in 2012. He served three terms before running for Senate in 2018. Though he lost to Republican Sen. Ted Cruz, O'Rourke gained notoriety and became a social media sensation for losing by a narrow margin in a deep-red state. Main issues: The Texan has spoken out on topics like immigration, taking a hard line against Trump's border wall. He has also supported gun safety, noted the importance of fighting climate change, saying he hasn't "seen anything better" than the Green New Deal, and supports universal health care, though he hasn't backed "Medicare for All."

Tim Ryan

Representative Tim Ryan, a Democrat from Ohio and 2020 presidential candidate, speaks during the Democratic Wing Ding event in Clear Lake, Iowa, U.S., on Friday, Aug. 10, 2018. Daniel Acker | Bloomberg | Getty Images

Age: 45 Announced bid: April 4 Who he is: Ryan is an eight-term congressman representing Ohio in the House. He is co-chair of the Congressional Manufacturing Caucus and serves on the House Appropriations Committee. He is best known for unsuccessfully attempting to unseat Rep. Nancy Pelosi as top the House's Democratic leader in 2016. Before being elected to the House, he served on the Ohio Senate from 2000 to 2002. Main issues: Ryan's campaign website says he's focused on rebuilding the economy to "work for all Americans" as the American Dream falls "too far out of reach." As a congressman he has worked on efforts to boost manufacturing and working-class Americans. He also cited issues like health care, education and veterans' care reform on his website.

Bernie Sanders

Senator Bernie Sanders (I-VT) Jay LaPrete | AFP | Getty Images

Age: 77 Announced bid: Feb. 19 Who he is: A self-described democratic socialist, Sanders is making his second attempt to be elected president after losing the Democratic nomination to Hillary Clinton in 2016. Sanders is not actually a Democrat — he's an independent who has been a senator from Vermont since 2007. Before being elected to the Senate, he served in the House from 1991 to 2007. Main issues: Sanders' top proposals include "Medicare for All" and free public college. One issue he has been most vocal about, though, is the growing wealth gap in the United States. To fix the wealth gap, Sanders proposed an estate tax for when someone leaves more than $3.5 million in assets to their heir.

Eric Swalwell

Rep. Eric Swalwell, D-Calif., speaks at a political event, Feb. 25, 2019, in Manchester, N.H. Elise Amendola | AP

Age: 38 Announced bid: April 8 Who he is: Swalwell is serving his fourth term as a congressman in the House. The California congressman, who has held his post since 2013, is on the House Intelligence and Judiciary Committees. Prior to his tenure as a congressman, he was on the Dublin, California, town council and was deputy district attorney in Alameda County. Main issues: Swalwell says that if he is elected president, he will look to tackle gun violence, health care and education reform in his first 100 days in office. Swalwell believes the U.S. should have no-interest federal student loans, tax-free employer contributions and debt-free college for public university students.

Elizabeth Warren

Sen. Elizabeth Warren, D-Mass. Tom Williams | CQ-Roll Call Group | Getty Images

Age: 69 Announced bid: Feb. 9 Who she is: Formerly an elementary school teacher and law professor, Warren has been a senator from Massachusetts since 2012. Specializing in bankruptcy law, she served as a special assistant to Obama for the Consumer Financial Protection Bureau from 2010 to 2011. Main issues: Warren wants to end corruption in politics by proposing reforms that would end lobbying and prevent senators and congressmen from trading stocks while in office. She is also looking to tax America's wealthiest citizens, having them pay a 2 percent tax on every dollar of net worth over $50 million, and pushing for the break up of big tech companies like Amazon and Facebook. She is another co-sponsor of "Medicare for All."

Marianne Williamson

Marianne Williamson attends the Project Angel Food's Angel Awards 2015. Araya Diaz/Getty Images for Project Angel Food

Age: 66 Announced bid: Nov. 16, 2018 Who she is: Williamson is a best-selling author, spiritual coach and activist. She unsuccessfully ran for a California seat in the House in 2014 but is best known for being Oprah Winfrey's spiritual advisor. She also founded a number of advocacy organizations, including Project Angel Food. Main issues: Williamson proposed a $200 billion to $500 billion plan for slavery reparations. Her campaign website says an "esteemed" council of black leaders would determine which educational and economic projects the money would be granted to. She also wants to combat climate change and enforce gun safety laws.

Andrew Yang

Andrew Yang Daniel Acker | Bloomberg | Getty Images