To beat US President Donald Trump, most political analysts agree the Democratic nominee is going to have to do two things:

- Build a broad coalition of Democratic voters who turn out to vote in large numbers.

- Win over independent voters, especially in states that could decide who gets the 270 Electoral College votes needed to become president, like a Michigan, Wisconsin, Pennsylvania and Florida.

Can Senator Bernie Sanders, the current front-runner who describes himself as a democratic socialist, do that? Anyone who says they know the answer doesn't.

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But here are some data points from recent national polls and from his dominant performance in the Nevada caucus to help us look closer at this question.

1) Sanders won in Nevada with an expanded coalition

Young voters, liberal voters and Hispanic voters all went decisively for Sanders, according to entrance poll results. Nationally, he leads by double digits among women and men in a recent Washington Post-ABC News poll of Democrats. He is currently tied with former Vice-President Joe Biden in polls that ask whom people would vote for in the general election for president, a Democrat or Trump.

But: The big test for Sanders will be South Carolina's primary on Sunday NZT, where the Democratic electorate is made up of a majority of black voters. An influential black member of Congress from South Carolina, James Clyburn, expressed scepticism of how Sanders will do there.

"I do believe it will be an extra burden for us to have to carry," Clyburn told ABC News yesterday of Sanders embracing socialism. "This is South Carolina, and South Carolinians are pretty leery about that title socialist."

Still, there's evidence that Sanders is scaling Biden's supposed firewall with black voters. In Nevada, Biden won their support, but Sanders still got 27 per cent of their vote, not an easy feat in a very crowded field. Outside of Nevada, the Post-ABC poll finds Sanders has more than doubled his support among black Democratic voters since January, support that has been driven by younger black voters who prefer him over Biden.

2) Democrats are becoming more okay with the idea of government-run healthcare

With Senator Elizabeth Warren, tiptoeing away from it, Sanders is alone on the debate stage embracing replacing private insurance with government-run health insurance. But in Nevada, entrance polls showed a clear majority of those going to caucus supported Medicare-for-all.

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Nationally, Democrats seem more okay with it, too. Sanders has made his campaign synonymous with Medicare-for-all. In the Post-ABC poll, 62 per cent of Democratic-leaning adults say Sanders is "about right" on the liberal spectrum, putting him on par with more moderate candidates who oppose it, like Biden and former South Bend, Indiana, mayor Pete Buttigieg.

3) Democrats are becoming more comfortable with the 's' word

Unlike a pure socialist, Sanders doesn't want government-run everything. But he argues that programmes like Medicare and Social Security are a form of socialism Americans already have and love. Those programmes could be expanded to government-run healthcare and provide free public college and childcare.

His opponents argue that's not feasible and will cost more money than the US government has. Sanders has struggled to articulate how much all this will cost. He has also acknowledged it will require raising taxes on the middle class (though he argues they'll save money in the long run).

His opponents are also worried that Sanders as the nominee will cast a pall over the party, specifically hurting Democratic candidates for Congress by raising questions about where Democrats stand on socialism.

Polls show that among a Democratic electorate, Sanders could be gaining the upper hand in this debate. According to the latest Post-ABC News poll, Sanders is seen as the candidate most likely to beat Trump by Democratic-leaning voters regardless of his socialist title. Half of all Americans give a shrug when they are asked if it matters if he embraces socialist policies. That likely speaks to Sanders's years-long effort to normalise his politics.

But: There's no evidence Sanders's embrace of socialism will help him win voters, and there is evidence it could cost him voters in a general election.

The Post-ABC poll finds that 37 per cent of independents and 79 per cent of Republicans say Sanders' socialism makes it more likely they'll oppose him.

I heard that from some swing voters in New Hampshire before the primary. Darrell Wozniak, a 39-year-old financial adviser, told me he voted for Trump in 2016 and wants to vote for a Democrat, unless it's Sanders: "I'm not a big fan of Trump, but I am a big fan of business and finance - so that's my fear, if Bernie Sanders or Elizabeth Warren win, is the stock market."

That raises alarm bells for national Democrats who are calculating the White House will be won in more moderate states like Michigan, Wisconsin or Florida, where there's no evidence socialism is gaining traction.

4) Sanders does not have backing of the Democratic establishment.

And he often openly spars with them.

Senator Joe Manchin, a prominent voice for the moderate wing of the party, refused to say if he'd vote for Sanders if he were the nominee.

Republicans are already trying to use Sanders's ideology against him and the Democratic Party.

Not helping his case is Sanders himself, who yesterday praised former Cuban dictator Fidel Castro.