With the Republican convention finally gavelled to a close, the transformation is complete. America’s Republican Party has finished turning itself into an albatross around the throat of what should be one of its most electable presidential candidates in years.

You might not believe Mitt Romney could ever stake claim to a label like “electable” or that he could ever have claimed the mantle of moderation. No one could be blamed for thinking that: after presidential candidate Mitt Romney was forced to pander to the far Right to win his party’s nomination, few remember Massachusetts governor Mitt Romney. But that phantom of the past is worth remembering, for the stunning gap between today’s presidential candidate and yesteryear’s governor explains so much about the sorry state of American politics right now — and in future.

Only a few years ago, Romney was describing himself as a “progressive”. He publicly defended a woman’s right to choose on abortion. He backed “full equality” for gay and lesbian people. As Massachusetts governor from 2002-06, he supported a ban on assault weapons and championed an early version of what would become President Obama’s healthcare bill.

He took some tolerant positions on undocumented immigration, plotted an aggressive effort to combat climate change, and mounted a campaign to close corporate tax loopholes. Underscoring the crossover appeal of such moderation, the Republican was rewarded by getting elected governor in this most Democratic of states.

Now, just a few short years later, Romney calls himself “severely conservative”. He pushes a near-total ban on abortion and fights same-sex marriage. He opposes the most minimal gun control measures. He promises to repeal President Obama’s health care bill, crusades against undocumented immigration and derides serious efforts to curb climate change. And he proposes a massive corporate tax cut in a deficit-plagued country whose effective tax rate is already among the lowest in the industrialised world.

It’s easy to write this shift off as merely a spectacular example of political somersaulting — and when it comes to rhetorical twists and turns, Romney is an especially daring acrobat, even by American standards. However, the change represents something more profound — and more profoundly disturbing.

In the past, flip-flopping has traditionally been the hallmark of America’s post-primary period in election years. Essentially, candidates pulled to the poles by internal party feuds move to the centre in the presidential election, to appeal to the more diverse national electorate. For a Romney-type candidate, that would have meant a general election version of himself that burnished his more moderate Massachusetts record.

Instead, we are now watching a candidate who flip-flopped to the margins and away from the middle in the primaries continue to do so as November’s vote nears. Indeed in recent weeks, Romney has reiterated his hardline position on abortion and healthcare and selected Wisconsin Congressman Paul Ryan as his running mate — a man whose ultra-conservative record is as divisive as it is extreme. Romney’s convention speech last night may have strained to sound a more moderate note, but Ryan’s on Wednesday was unabashed in its confirmation of the party’s shift to the right.

Taken together, it suggests that Romney envisions a whole new road to the White House. Having seen the failure of John McCain’s party-snubbing image in 2008, Romney is calculating that in today’s bitterly polarised climate, he can no longer follow the old path of flipping back to his moderate image and cobbling together a winning coalition from the centre. Instead, his ultraconservative positioning shows he is betting that a Republican can only win a presidential election by mobilising his party’s hard-Right base.

This is why the long-term transformation of the Republican Party is so significant. Whereas the party’s old orthodoxy was ideologically rooted in a few ideals — lower taxes for everyone, smaller government, rhetorical support for equal opportunity — today’s party canon is a litany of bizarre and specific shibboleths. It backs everything from crushingly regressive taxation and intrusive policies banning abortion, to institutional discrimination on the basis of sexual orientation, to state anti-immigrant laws that effectively endorse racial profiling.

And unlike the GOP’s old ideals, which were wide enough to be seen as inclusive, today’s Republican agenda is increasingly narrow. As effective as it is at galvanising the party’s base, it is equally effective at turning off independent voters. In the context of the 2012 election, it exchanges Romney’s crossover appeal for a newfound base appeal — reducing his general electability in wide swathes of the country.

It also lets Obama off the hook. The President should have faced real questions in this election about why he sold out on so many policies (weak Wall Street reform, a healthcare bill that was simply a bailout to private insurance). Instead, Obama gets to run as the moderate economic populist.

Of course, Romney’s lurch to the Right doesn’t guarantee he will lose. While the Republican candidate’s mass appeal may be tarnished, the dire state of the economy may still ultimately seal Obama’s fate as a one-term President, no matter how unappealing Romney becomes.

Nonetheless, the relationship between Romney and his party highlights a longer-term problem. For the Republican Party, it means a nominating process that naturally selects less and less electable candidates, who must try to win with a narrower and narrower political coalition. For America at large, that means a national political discourse that moves farther to the Right than ever.

In this unfortunate future, this era’s conservative ethos will become the liberal Democratic position, in juxtaposition to the ever-more radical conservative position of tomorrow’s Republican nominees. That may result in more electoral wins for Democrats. But those would be Pyrrhic victories for an America that desperately needs a new definition of the political centre — one that is far more progressive than today’s status quo.

David Sirota is a contributor to Salon.com and author of Back to Our Future: How the 1980s Explain the World We Live In Now.