One week before the Iowa caucuses, Sen. Bernie Sanders Bernie SandersNYT editorial board remembers Ginsburg: She 'will forever have two legacies' Two GOP governors urge Republicans to hold off on Supreme Court nominee Sanders knocks McConnell: He's going against Ginsburg's 'dying wishes' MORE (I-Vt.) is growing in strength and increasingly looks like the favorite to win the Democratic nomination.

Polling in Iowa is still tight and shows a four-candidate race between Sanders, former Vice President Joe Biden Joe BidenMomentum growing among Republicans for Supreme Court vote before Election Day Trump expects to nominate woman to replace Ginsburg next week Video of Lindsey Graham arguing against nominating a Supreme Court justice in an election year goes viral MORE, Sen. Elizabeth Warren Elizabeth WarrenBiden's fiscal program: What is the likely market impact? Warren, Schumer introduce plan for next president to cancel ,000 in student debt The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon MORE (D-Mass.) and former South Bend, Ind., Mayor Pete Buttigieg Pete ButtigiegBipartisan praise pours in after Ginsburg's death Bogeymen of the far left deserve a place in any Biden administration Overnight Defense: Woodward book causes new firestorm | Book says Trump lashed out at generals, told Woodward about secret weapons system | US withdrawing thousands of troops from Iraq MORE, making it clear the first-in-the-nation caucus battle remains anyone’s game.

Yet it is also clear that Sanders has a strong chance of coming out on top in Iowa, as well as in New Hampshire, which will vote just a week later.

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Such a result would make him the clear front-runner, and would likely unnerve parts of the Democratic Party uneasy about the progressive independent being their standard-bearer in the fall.

Sanders separated himself from the pack in a New York Times-Siena Research poll of Iowa released over the weekend, one of the first to find a clear-cut leader in the Hawkeye State. And a WBUR survey of New Hampshire released this week found Sanders opening up a 12-point advantage over the next closest contender.

Sanders surpassed Biden in CNN’s latest national poll, marking the first time Biden has not held the top spot in that poll this cycle.

Biden is ahead of Sanders in Nevada and South Carolina, which host the party’s third and fourth contests. But victories in the first two states could propel Sanders.

And Sanders is also prepared to put up a fight on March 3, when more than a dozen contests will be held on this cycle’s Super Tuesday.

A new survey out of California, where more delegates are at stake than anywhere else, found Sanders with 4-point lead over Biden, a sign of his popularity in a key Super Tuesday state.

Sanders has raised the most money, the left appears to be coalescing behind him and his base of young supporters is energized and more racially diverse than it was in 2016.

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If there’s a downside for Sanders, it is that he is marooned in Washington for President Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE’s impeachment trial. Yet he’s being buoyed on the ground in Iowa by his progressive allies in “the squad” and from his unmatched levels of support from the actors, artists and pop culture heavyweights lining up behind his campaign.

“It’s Bernie’s race to lose,” said one Democrat who has raised money for Biden.

The landscape could still change dramatically once voters begin casting ballots.

Biden has been a sturdy and underestimated front-runner for more than a year and outside of the CNN survey, he has held the top spot in most national polls.

The former vice president’s broad base of support among black voters makes him the favorite to win South Carolina and should keep him competitive across the Deep South on Super Tuesday.

“I still think Joe wins,” said Howard Gutman, a former ambassador and Democratic strategist who has endorsed Biden for president. “It’s not going smoothly but it will be enough to get him home.”

Warren could see a burst of momentum coming out of Iowa if she beats expectations there. And establishment Democrats are signaling that they’ll rally to defeat Sanders if he continues to gain momentum.

“The floodgates are about to open and every establishment Democrat is going to be warning that Bernie will get killed in the general election,” the Democratic fundraiser said.

But as Warren has faded, Sanders has accumulated new support from the left and is in a prime position to become the party’s progressive standard bearer.

Sanders has been winning endorsements from key progressive groups, including up-and-coming organizations run by young people, such as the climate-focused group Sunrise Movement and Dream Defenders, which organizes on behalf of people of color.

When 18 liberal groups banded together last week to pledge their commitment to electing a progressive candidate, seven of those groups had already endorsed Sanders, compared to two for Warren. The rest remain neutral.

And while most national labor groups are on the sidelines, Sanders has earned the backing of key local unions pledging to work on his behalf in early-voting states.

This month alone, Sanders has won endorsements from the Clark County Education Association in Nevada, the nation’s largest independent educator union, and the SEA/SEIU Local 1984, the second largest union in New Hampshire, where Sanders leads in most recent polls.

Democratic strategist Michael Gordon, principal of Group Gordon, said Warren fumbled on "Medicare for All," the premier policy issue among progressives, opening the door for Sanders to cement his standing on the left.

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“Sanders has the stronger standing in the progressive community overall,” Gordon said. “He’s been out there longer and people believe what says. It’s been strange for Warren, because she has such well thought out policy positions. But she didn’t think health care through and she’s paid the price for it ever since.”

With new momentum, come new attacks.

Hillary Clinton Hillary Diane Rodham ClintonJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Momentum growing among Republicans for Supreme Court vote before Election Day Warning signs flash for Lindsey Graham in South Carolina MORE unloaded on Sanders this week, relitigating her grievances from the 2016 campaign and describing him as an unlikeable “career politician” whose supporters “got sucked into” backing him.

But unlike 2016, when Clinton entered the race with a nearly insurmountable lead, there are no superdelegates tilting the playing field against Sanders. The Democratic National Committee has committed to running a fair and open primary after complaints from Sanders over the 2016 cycle.

The anti-Sanders crowd has been looking to make the case that he would be a disastrous general election candidate.

“I think it's very clear to me that with these swing voters that I care about — the Trump-Obama voters in the Midwestern states — Bernie Sanders is not the candidate we need to beat Donald Trump in November,” Jim Messina, former President Obama’s 2012 campaign manager, said this week on MSNBC.

Sanders’s allies say they’re not sweating the brushback. They point to polls showing Sanders running neck-and-neck with Trump in a hypothetical general election race. Sanders matches Biden as the candidate who appears, at least on paper, to perform best against Trump.

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And Sanders seems to have broader appeal within the Democratic Party this time around, compared to 2016 when many mainstream Democrats were turned off by his anti-establishment rhetoric and he struggled mightily to attract support from racial minorities.

The latest Morning Consult survey found that 74 percent of Democrats have a favorable view of Sanders, compared to only 16 percent who view him negatively. And the latest CNN survey found Sanders pulling ahead of Biden for the first time among nonwhite voters.

“If [the anti-Sanders crowd] doesn’t go after him soon it’ll be too late,” said Gordon. “Look at Trump and the Republicans from four years ago. A lot of Republicans held back because they didn’t think he’d be nominee, then he racked up wins and it was too late. So do it now or else get in line and support him enthusiastically if he’s candidate.”