(Reuters) - February kicks off the presidential nominating contest for both the Democratic and Republican parties.

FILE PHOTO: Democratic 2020 U.S. presidential candidates Senator Elizabeth Warren (D-MA) speaks with former Vice President Joe Biden and Senator Bernie Sanders (I-VT) listening at the seventh Democratic 2020 presidential debate at Drake University in Des Moines, Iowa, U.S., January 14, 2020. REUTERS/Shannon Stapleton/File Photo

For Democrats, what was once a field of more than 20 candidates has been whittled to a dozen. The Republican choice will almost certainly be President Donald Trump.

DEMOCRATIC CONTENDERS

JOE BIDEN

Biden, who was vice president under President Barack Obama, has largely stayed atop the Democratic field for months, arguing that his more than 40 years in elected office makes him best suited to take over for Trump on day one.

Questions persist about his age (77) and his moderate brand of politics, which progressives claim are out of step with the leftward drift of the party.

Trump’s apparent effort to push the Ukrainian government to investigate Biden and his family served to boost Biden’s argument that Trump views him as a top threat.

So far, Biden’s greatest asset has been his ability to assemble a diverse coalition of supporters that includes African Americans, Hispanics and working-class white voters, which ensures he will likely go deep into the nominating contest.

ELIZABETH WARREN

The 70-year-old U.S. senator from Massachusetts has emerged as a top threat to Biden and remains the highest-polling woman candidate in the race. A fierce critic of Wall Street, she has based her campaign on a populist anti-corruption message and argues the country needs “big, structural change.”

Despite her liberalism, she has been criticized by some progressives for not fully embracing the “Medicare for All” healthcare plan that would eliminate private insurance in favor of a government-run plan. Some moderates, on the other hand, view her policies, which include a tax on the super-rich, as too extreme.

Even so, Warren contends that she is the best candidate to unite the party’s warring moderate and progressive factions.

BERNIE SANDERS

The irascible U.S. Senator from Vermont with an impassioned following is making a second attempt at the presidency – and remains among the top tier of candidates.

As in his first presidential run in 2016, Sanders, 78, has campaigned as an unapologetic, self-described democratic socialist who seeks nothing less than a political revolution.

Sanders, whose signature issue is government-run universal healthcare, has again proven to be a fundraising powerhouse, leading the field in terms of total campaign contributions.

PETE BUTTIGIEG

For a candidate who came into the race largely as a political unknown, the 38-year-old former mayor of South Bend, Indiana, has shown surprising staying power, particularly in the early voting states of Iowa and New Hampshire.

A Midwestern moderate and Navy veteran, Buttigieg has billed himself as the torchbearer of a new political generation, but ironically has engendered skepticism among young voters in the party, who view him as insufficiently liberal.

Should he prevail in the Democratic race, he would be the first openly gay presidential nominee in U.S. history.

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MICHAEL BLOOMBERG

Former New York City mayor and media mogul Bloomberg, 77, surprisingly announced his candidacy in late November. He had said in March that he would not make a run for the White House.

In an unusual move, Bloomberg is skipping early voting states, focusing instead on the larger states such as California, Florida and Texas that vote on March 3 - Super Tuesday - and beyond.

Ranked by Forbes as the eighth-richest American with an estimated worth of $53.4 billion, Bloomberg has already spent more than $200 million of his fortune on his campaign, more than what his entire Democratic rivals combined have spent in the past year.

Bloomberg had previously been praised within the party for his advocacy and philanthropy on climate change and in fighting gun violence. Bloomberg served as mayor of New York from 2002 to 2013.

AMY KLOBUCHAR

The U.S. senator from Minnesota has focused much of her campaign on winning the neighboring state of Iowa, presenting herself as a pragmatic alternative to the likes of Sanders and Warren and charming voters with a self-effacing sense of humor.

Klobuchar, 59, has also consistently qualified for Democratic debates, which has helped keep her candidacy viable. She was further boosted when the New York Times recently endorsed her – along with Warren – for the nomination.

But Klobuchar is running out of time - and a poor showing in Iowa will likely sink her campaign.

ANDREW YANG

The New York entrepreneur and former tech executive is focusing his outsider campaign on an ambitious universal income plan. Yang, 45, wants to guarantee all Americans between the ages of 18 and 64 a $1,000 check every month.

The son of immigrants from Taiwan, Yang calls automation the biggest threat facing U.S. workers. He has built a small but enthusiastic following, particularly on social media.

TULSI GABBARD

The Samoan-American congresswoman from Hawaii and Iraq war veteran is the first Hindu to serve in the U.S. House of Representatives and has centered her campaign on her anti-war stance.

Gabbard’s populist, anti-war approach has won her fans among the far left and the far right.

Gabbard, 38, has been engaged in a public feud with former Democratic presidential nominee Hillary Clinton. She sued Clinton for defamation, seeking at least $50 million in damages for suggesting last year that one of the party’s White House contenders was a “Russian asset.”

TOM STEYER

A billionaire environmentalist and force in Democratic fundraising over the past decade, Steyer, 62, is another candidate trying to leverage his personal fortune into public support but has been less successful than Bloomberg in that regard.

Steyer did surprise observers by qualifying for the January presidential debate in Iowa – and his money may allow him to stay in the race longer than other fringe candidates.

JOHN DELANEY

The former U.S. representative from Maryland became the first Democrat to enter the 2020 race, declaring his candidacy in July 2017. Delaney, 56, says that if elected, he would focus on advancing only bipartisan bills during the first 100 days of his presidency.

A former business executive, Delaney is self-funding much of his campaign, but has seen almost zero support in polls.

MICHAEL BENNET

Bennet, 55, a U.S. senator from Colorado, has based his political career on improving the American education system. He previously ran Denver’s public schools.

During a partial U.S. government shutdown in January 2019, he garnered national attention criticizing Republicans for stopping the flow of emergency funds to Colorado.

DEVAL PATRICK

Patrick was a late entry to the race, announcing his candidacy in November just days before early-state filing deadlines. The 63-year-old former Massachusetts governor said he was seeking to draw in Americans who felt left behind and to bridge a party he saw split between “nostalgia” or “big ideas” that left other voices out.

His bid has received little media coverage and has not made a dent in polls.

REPUBLICANS

DONALD TRUMP

Trump is the clear favorite to win the Republican nomination, and there has been criticism among his opponents that party leadership has worked to make it impossible for a challenger. Still, the incumbent will face at least two rivals.

Since his surprise win in the 2016 presidential election, Trump, 73, has become a ubiquitous political force, both through the controversies he generates almost daily and his prolific Twitter account.

Trump was impeached in the House of Representatives for his request that Ukraine carry out investigations into his political rival, Joe Biden and his son Hunter. But the U.S. Senate is expected to acquit him in a trial now underway.

Trump is focusing his re-election message on the strong economy, while continuing the anti-immigration rhetoric that characterized his first campaign.

JOE WALSH

A former congressman, Walsh, 58, has become a vocal critic of Trump.

Walsh won a House seat from Illinois as a candidate of the Republican Party’s fiscally conservative Tea Party movement in 2010 but was defeated by Democrat Tammy Duckworth in his 2012 re-election bid. After leaving Congress, he became a Chicago-area radio talk-show host.

BILL WELD

The 74-year-old former Massachusetts governor ran unsuccessfully for vice president in 2016 as a Libertarian. He has been a persistent critic of Trump, saying when he began his 2020 campaign that “the American people are being ignored and our nation is suffering.”