A self-proclaimed socialist like Bernie Sanders will always be an oddity in American politics; one who polls so well in Iowa and New Hampshire doubly so.

But what was so odd about the Democratic debate on Tuesday was not the socialist; it was how little his opponents disagreed with him. Particularly Hillary Clinton, whose career has always been built on, well, Clintonian triangulation. Hillary's lurch to the left is by now well-documented. There's her support for immigration amnesty and tougher gun control measures. When those scandalous Planned Parenthood videos emerged, she initially expressed concern — old habits die hard — before veering toward a full-throated embrace of the pro-choice gospel. And, of course, there's her flip-flop on the TPP free trade deal, which she herself negotiated and now opposes, as well as her newfound opposition to the Keystone pipeline.

It remains to be seen, of course, whether this progressive scramble is merely a primary gambit, to be discarded for studious centrism once Clinton can decorate her desk with Bernie's bleached skull, or whether it is her true political strategy. But remember, her lurch to the left began before Sanders' meteoric rise in the polls.

So let's step back from Clinton's switcheroos for a moment, and consider the two overarching but competing narratives of the past eight years of American politics.

One is that — as was true in the Nixon, Reagan, Clinton, and Bush eras — America remains a basically center-right nation, and Democrats cannot win nationally unless they are centrists. Obama's electoral success, in this view, is mostly a combination of luck — as in, he benefited from exasperation over George W. Bush, the timing of the financial crisis, and Mitt Romney's missteps — and his outstanding political skills. America may be trending leftward, but not that much, and not that quickly. Obama's inability to govern once he lost his 2008-2010 Congressional supermajority shows that.

The competing narrative says that America really is becoming a much more progressive nation. The increasing secularization, or at least unchurching, of the U.S. makes America's middle much more friendly to progressive social issues — witness the stunning success of the same-sex marriage movement. The uncertainties associated with globalization and technological change, and the increasing atomization of American society, increase the demand for a safety net. The 2012 election, after all, was basically about ObamaCare, and Obama won. In this view, America's changing demographic mix is creating an emerging majority "rainbow coalition" even as Republicans are locked in a deadly vicious cycle of relying evermore on supermajorities of the shrinking white vote to remain competitive nationally, turning off everyone else in the process. Obama really was a "New Reagan," a figure who not only won political successes for himself, but also changed the political balance of power for the country.

Of course, which of those narratives you believe is going to change how you behave as a political actor. Many conservatives actually believe the second narrative, leading to the overpowering smell of desperation to their various reckless attempts to frustrate the progressive agenda. Obama probably believes the second narrative. And the Democratic debate certainly gave the impression that the Democratic Party itself believes the second narrative.

But objectively, which narrative is more true? Beats me. I'd say they're both true, probably.

The Democratic Party, however, seems to have decided to run its 2016 strategy based on the second narrative. That is a generation-defining bet. If the Democratic nominee runs as an avowed left-winger, betting on the rainbow coalition — and the women's vote in Clinton's case — and is up against a smart, charismatic, moderate-sounding, gaffe-avoiding Republican nominee (Arco-may Ubio-ray), and it turns out that the conservative-friendly narrative is actually more right than the liberal one — well, the Democratic Party is looking at an epochal defeat.

If, on the other hand, the Democratic nominee runs as an avowed left-winger, and the progressive narrative is right, and the GOP nominates an underwhelming candidate (looking at you, Jeb), well, then of course the Dems will win the Big Prize: not just the White House and a chunk of Senate seats, but convincing evidence that America really is trending leftward, that it really is different this time, that we have entered a new era of American politics.

Obviously, as a conservative, my hope is that the Democratic Party makes that bet in grand style, and loses hugely. But in any case, it will certainly be fun to watch.