One of the leading candidates for President in the US is a socialist.

We all know about Donald Trump and his mad plans to do mad things, fired by a madness rich and deep.

But there’s someone else in the US Presidential race who is even further from the American mainstream and who could be even more influential.

Vermont Senator Bernie Sanders is ahead of Hillary Clinton in the poll for the New Hampshire primary – the vote to select the Democrats presidential candidate. He leads 44-37.

New Hampshire is the first primary vote held and is therefore seen as a key marker in the Presidential race. It gets a vast amount of media attention. The last seven Presidents have all come first or second in their New Hampshire primary.

Sanders is currently ranked about third for odds of winning in 2016. He’s rated by the betting agencies as having about a 7 to 8 per cent chance of becoming president. That maybe doesn’t sound like a lot, but at this stage of the process when the field is littered with contenders, it’s pretty good. Only Jeb Bush and Clinton are ahead of him.

All this matters because Sanders is not another cookie-cutter centrist. He offers real policy alternatives. He’s genuinely left-wing. (A socialist in American terms although maybe not by the criteria of the rest of the world)

For example, these are from his 12-point agenda for America, on his website:

Trade Policies that Benefit American Workers: We must end our disastrous trade policies (NAFTA, CAFTA, PNTR with China, etc.) which enable corporate America to shut down plants in this country and move to China and other low-wage countries. We need to end the race to the bottom and develop trade policies which demand that American corporations create jobs here, and not abroad.

Taking on Wall Street:  The greed, recklessness and illegal behavior of major Wall Street firms plunged this country into the worst financial crisis since the 1930s. They are too powerful to be reformed. They must be broken up.

Growing the Trade Union Movement: Union workers who are able to collectively bargain for higher wages and benefits earn substantially more than non-union workers. Today, corporate opposition to union organizing makes it extremely difficult for workers to join a union. We need legislation which makes it clear that when a majority of workers sign cards in support of a union, they can form a union.

Those are not the kind of things other Democrats are proposing.

Now, I’m not saying that Mr Sanders will beat Hillary Clinton. One poll ahead of one primary is not enough. Endorsements also matter and on that front Hillary Clinton is miles ahead.

But the way politics works is that a successful candidate with more extreme views pulls the whole field in their direction.

In US politics, the primaries see candidates tack out to the political extremes as they chase the votes of the party members who vote in primary elections. They then tack back to the middle as they chase the votes of ordinary citizens in the actual presidential election.

But the process of winning the primary forces a candidate to nail some colours to the mast. Sanders’ success will pull Clinton to the left as she tries to neutralise him. That effect will fade after she beats him, but it can’t be erased completely.

And as the two eventual candidates face off for President, trying to capture the centre, Clinton’s extra leftness will pull the eventual Republican nominee slightly leftward too.

So even if he loses the Democratic nomination, the effect of Sanders’ run will be to shift the whole of the US ever so slightly to the left.