The battle of principles versus pragmatism we are witnessing between Bernie Sanders and Hillary Clinton has direct relevance to how Australia's parties operate, and offer lessons for how we can get things done, writes Tim Dunlop.

Earlier this week, Bernie Sanders ran away with the New Hampshire primary, winning convincingly over Hillary Clinton. As the fight for the Democratic nomination continues, a key issue that remains between the two candidates is the matter of electability.

Essentially, the argument has come down to a contest between Clinton's "realism" and Sanders' call for a political revolution. Clinton presents herself as the hard-nosed centrist, saying:

I don't believe you change hearts. I believe you change laws, you change allocation of resources, you change the way systems operate. You're not going to change every heart. You're not.

Sanders, on the other hand, says the real problem is that Clinton - like Obama before her - threw her lot in with big-money interests, specifically with Wall Street. Therefore, by default, she will end up doing the bidding of those big-money interests. Nothing in Washington changes because the same people are paying the piper.

By not taking that money, Sanders argues, he avoids the trap. He is betting that he will instead be able to mobilise a frustrated army of disaffected voters who actually want the things he is offering, such as universal health insurance, regulation of the financial sector, increased taxes on the wealthy, and free college tuition. As Sanders has said:

The major political, strategic difference I have with Obama is it's too late to do anything inside the Beltway. You gotta take your case to the American people, mobilise them, and organise them at the grassroots level in a way that we have never done before.

In a democracy, all of this is an entirely legitimate argument, and it is fascinating to watch Sanders and Clinton argue the toss, not least because of its relevance to Australia.

Indeed, the same argument drives a lot of debate in our politics, particularly between the Greens and the Labor Party. On everything from coal mining to climate change to asylum seekers, the Greens present themselves as the party of principle and they disparage the willingness of Labor to compromise in the name of electoral expediency.

For instance, the Greens and other progressive voices make a totally valid point in saying that Labor often ends up sounding - and more importantly, acting - pretty much the same as the Liberal-National Party Coalition. Rather than enhance Labor's electoral prospects, this strategy can actually diminish them, in that people inclined to those sorts of policies are likely to reject Labor's "Coalition lite" pitch and instead go with the real McCoy.

Progressives also argue that this expediency humiliates and discourages Labor's grassroots, causing them to either abandon the party altogether or to at least stop openly supporting them, ceding the public sphere to their opponents. Part of the significance of Julia Gillard's misogyny speech, for example, was that it reignited supporters who had been significantly discouraged by her position on equal marriage and asylum seekers.

In other words, it is hard to get your supporters to publicly endorse your progressive policies if you are also pursuing policies that embarrass them.

There is another point to make: compromise is often sold as the "sensible middle", a rational halfway point between extremes. But this is bogus too. You only have to look at major-party bipartisanship on asylum seekers to see that such compromise, such expedience, far from being moderate, can lead to ugly, extremist policy, exactly as we have now.

But perhaps the strongest argument in favour of pursuing principled positions and eschewing "pragmatism" is that it is the only way of shifting the centre of any given debate.

To understand this, you have to realise that the political centre is not some pre-existing mid-point between the policies of the left and right, but the contested space in which majority support is formed. By fighting for the "extremes", you shift the centre.

Equal marriage is a classic example. Had people meekly curled up like good centrists and accepted the pragmatic position of people like Clinton and Gillard, public opinion would still be against marriage equality. Instead, both here and in the US, thanks to relentless, principled argument, polls show majority opinion now favours a position that was once considered extreme.

And notice: despite Clinton's pragmatic mantra, hearts were changed first. The law change came later.

Another example is asylum seekers. Federal Labor argue, in part, that they are forced to adopt a hard line on the matter because the community demands it. But at the moment, state governments of all persuasions - governments that rely on the same voters to elect them - are saying openly that they are willing to accept asylum seekers listed for removal to offshore detention.

Surely this indicates there is a debate to be had, that people are open to persuasion? Changing minds on this would not be easy, but that is hardly the point.

The point is, if you constantly compromise your position on hard issues, you not only start to resemble your opponents, you close down the range of possible debate. You compromise your principles and lose the argument.

But before we start feeling too morally superior about sticking to our principles come-what-may, there is another aspect to all this.

The weakness with the principles-at-any-cost approach is that, at some point, refusing to budge on your position becomes anti-democratic. We see this most obviously with the Tea Party candidates who are willing to shut down the US government rather than compromise on their alleged principles. We see it with members of the Coalition who have demanded a plebiscite on equal marriage and then have said they will not abide by the outcome if it doesn't suit them.

Such an approach is not principled. It is a form of totalitarianism.

Compromise is often considered a dirty word in politics, but in a democracy, compromise is necessary. This is not because of some jaded concession to getting votes, some cynical selling out of your true principles, but because people are different and a democracy has to respect different views.

Indeed, recent comments by Greens' Leader Senator Richard Di Natale, highlight the point. He said:

My view is you are in politics to get outcomes... (and that) there is some common ground that we will be able to work with the government on.

Such an approach is neither selling out nor necessarily a shift to the centre: it is a recognition of democratic reality.

It is simply a fact that people of goodwill can have different, strongly held and conflicting - even incommensurable - opinions on major issues. In a democracy, to insist that only yours are right in all circumstances is the truly unprincipled position.

Still, my inclination is that the Sanders-Greens side of the argument is stronger: the forces of conservatism and the status quo are so powerful that only a certain sort of progressive ruthlessness has any chance of holding the line against it.

Nonetheless, this is the democratic paradox: inflexibility and compromise are both essential to the process. To put it another way, we need people to stick to their political principles come-what-may so that we get a better quality of compromise. Welcome to grey.

Tim Dunlop writes regularly for The Drum and a number of other publications. He hosts the podcast Washington Dreaming, discussing the forthcoming US presidential election. His new book, Busted Utopia: The Future of Work, Rest and Play will be released in 2016. You can follow him on Facebook.