In the United States, a full presidential term lasts four years. Not even halfway through Republican Donald Trump’s tenure as president, Democratic candidates have had the next election in their sights.

Unseating an incumbent president after only four years is a tough task—the most recent occurred in 1992, when Democrat Bill Clinton defeated Republican incumbent George H. W. Bush. So, what makes Democrats enthusiastic about the 2020 election?

The answer lies within the potential candidates. After the 2016 campaign had only three viable candidates, the assortment of people that have been strong theoretical candidates is akin to the Republican grouping of 2020.

While only one candidate has formally declared his candidacy as of now, there are others that have recently expressed interest. The official field will likely not be known until mid-to-late 2019.

Despite that, here are numerous candidates that could pursue the 2020 presidential nomination of the Democratic Party:

Declared

John Delaney | House Representative, Maryland’s 6th District, 2013—Present

The only officially declared candidate as of today, the Maryland congressman announced his candidacy in an op-ed featured in The Washington Post in July 2017. Attempting to capitalize on name recognition was Delaney’s prime reason for announcing merely months after Trump took office.

Delaney, retiring from Congress in 2018 after serving since winning in the 2012 election, does not feature much political experience after, what would be, six years in the House of Representatives. Prior to politics, Delaney was a successful businessman, winning the Ernst & Young Services Award for the Mid-Atlantic region in 2004 for his work with CapitalSource. According to Roll Call, Delaney is the third richest member of Congress.

As seen in a recent commercial released in Iowa during Super Bowl LII, Delaney is a firm believer in bipartisanship. According to his aforementioned op-ed, his platform primarily relies on creating new infrastructure, which will be funded via Delaney’s “bipartisan approach to infrastructure and international tax reform”.

Publicly Expressed Interest

Joe Biden | Vice President, 2009—2017

After wide assumption that he would run, the former vice president passed on the 2016 election due to the passing of his son, Beau. However, after recent developments in the Trump administration, many of Biden’s aides told Politico that it wasn’t out of the question for Biden to run in 2020.

Biden, currently on tour promoting his book “Promise Me, Dad,” has most recently served as Vice President of the United States under Barack Obama’s two terms. Prior to that, he served as senator of Delaware for 36 years.

Julian Castro | Secretary of Housing and Urban Development, 2014—2017

Currently out of office, Castro was most recently the Secretary of Housing and Urban Development in the Obama administration. Before ascending that office in 2014, Castro worked in his hometown of San Antonio, Texas for 13 years—including five as mayor.

Eric Holder | Attorney General, 2009—2015

Staying out of the public eye, Holder currently works as a private practice attorney. He returned to private practice work after serving as Barack Obama’s first attorney general, resigning in 2015 for ‘personal reasons’.

John Kerry | Secretary of State, 2013—2017

Kerry is one of the most experienced members on this list. Most recently serving as Barack Obama’s Secretary of State from 2013 to 2017, Kerry also served as a Senator from Massachusetts for 28 years. Kerry also previously ran for President in 2004, securing the Democratic nomination over candidates such as John Edwards and Howard Dean. Kerry was defeated by the incumbent, George W. Bush, in the general election.

Part II of likely 2020 Democratic candidates will be released next week.