U.S. Democratic presidential candidates: Who's in so far

The 2016 U.S. presidential race is heating up on the Democratic side, as declared and potential candidates begin carving their road to Washington.

• U.S. Republican presidential candidates: Who's in so far

Here are some of the bignames whoare,or may,be in the running to replace U.S. PresidentBarackObama:

Lincoln Chafee

Lincoln Chafee, who sat in the U.S. Senate as a Republican, later won the governor's job inRhode Island as an independent before undergoing yet another political shift and becoming a Democrat in 2013.

Chafee was the only Senate Republican to vote in 2002 against the U.S. invasion of Iraq and he says on his campaign websitethat hewantsthe U.S. to make "international decisions with brains and not biceps."

Chafee, 62, also has some experience in Canada the trained farrier spent seven years working as a blacksmith at racetracks in the U.S. and Canada, his campaign bio says.

Hillary Clinton

A former senator, secretary of state and stillwife of ex-president Bill Clinton, Hillary Clinton is the undisputed front-runner for the presidential nomination. The problem for Clinton is that she was also the front-runner in 2007, before a junior senator from Illinois overtook her during the primary and later became president.

After announcing her candidacy on April 12 with a video clearly intended as an appeal to middle-class voters, Clinton said her campaign is "taking nothing for granted." She's travelling by road to early primary states to parlay her message that"the deck is still stacked in favour of those at the top" and that she wants to be a "champion" for the American people.

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Clinton's policy stancesarelargelyin lock-step withthe socially progressive approachofObama, particularly on issues such ashealth care and climate change mitigation.As secretary of state, however,she advocated a more aggressive approach to some foreign crises for example, sheargued in favour of arming some rebel groups at the outset of theSyriancivil war, a move that Obama resisted until last year.

Clinton recently came under fire from critics on both sides of the aisle after it was revealed she used a private email server and account during her time as secretary of state.

Martin O'Malley

Martin O'Malleywas elected mayor of Baltimore at 36yearsold and went on to serve two consecutive terms as the governor of Maryland from 2007 to 2015. Now 52, the telegenic father of four isseen among Democrats asa more liberal alternative to Hillary Clinton and a seasoned, smooth operator on the campaign trail.

Recently, O'Malley has become a vocal critic of political dynasties in the U.S. thinly veiled references to the Clinton and Bush families despite having campaigned aggressively for Hillary Clinton during her 2008presidential bid. In an interview with ABC earlier this year, O'Malley said that "the presidency is not some crown to be passed between two families.

"It is an awesome and sacred trust to be earned and exercised on behalf of the American people."

While his is a long-shot candidacy, O'Malley had considerable legislative successes during his time as governor in Maryland. His most notable accomplishments include a minimum wage increase, a repeal of the state's death penalty law and sweeping gun-control measures.

Bernie Sanders

Bernie Sanders first gained national attention as the "socialist mayor" of Burlington, Vt., during the Reagan era of the 1980s.

In 1990, he was elected to the U.S. House of Representatives, where he sat until he was elected to the U.S. Senate in 2006. He ran as an independent, but was endorsed and supported by the Democratic Party. Sanders still sits as an independent, but caucuses with the Democrats in the Senate.

Sanders has great popularity in Vermont. He has pledged not to run a negative ad and says he will run an issues-oriented campaign. "The major issue is, how do we create an economy that works for all of our people rather than a small number of billionaires?"

He then identified his second issue when declaring his run for the nomination: "A political situation where billionaires are literally able to buy elections and candidates."

Should Sanders, 71, win the Democratic Party's nomination and then the presidency, he would replace former president Ronald Reagan as the oldest when inaugurated.

• Vermont Senator Bernie Sanders announces presidential bid

Jim Webb

Former Virginia Sen. Jim Webb announced his presidential campaign on July 2. After his outspoken opposition to the 2003 invasion of Iraq, he was recruited to run for the Democrats in Virginia in 2006, then stepped down after just one term.

Webb says he has a "pretty diversified" professional life. He has been a much-decorated marine officer in Vietnam, Secretary of the Navy, an assistant secretary of Defence, U.S. Congress counsel and served on several committees, including foreign relations and armed services, while in office. He's also done work as a filmmaker, authored 10 books and won an Emmy for his work as a journalist.

• Jim Webb joins Democratic race for U.S. presidential nomination

Possible candidates

In the Democratic Party, there are efforts to get Vice-President Joe Bidento challenge his former cabinet colleagueClinton for the nomination. Biden, 72, hadsought the Democratic presidential nomination in 1988 and 2008, but was not successful.

Also of note is Massachusetts SenatorElizabeth Warren, a highly progressive academic turned politician. Warrenheaded the congressional panel charged with overseeing the distribution of bailout fundsfollowing the 2008 financial crisis,and has championed financial sector reform and stricter regulations on banks. Despite her saying in March,"I am not running and I am not going to run," liberal groups MoveOn.org and Democracy in Action are still pushing for her to run.