There’s no question that former Massachusetts governor Mitt Romney was vulnerable in this year’s Republican presidential primary.

After all, he had signed a health care law in Massachusetts that bore more than a passing resemblance to the national law championed by President Obama. Romney had also switched his position on abortion — from pro-choice to pro-life — and was an uneasy fit (at best) for the sort of economic populism sweeping the country. He’s also a Mormon in a party whose primary electorate is dominated by white evangelical Protestants.

Former Arkansas governor and current Fox talk-show host Mike Huckabee on the set of his show "Huckabee" at Fox News headquarters in Manhattan.

Romney has, without doubt, run the best campaign of anyone in the race; he’s been disciplined about message and money, avoiding many of the pitfalls that laid him low in 2008.

But he’s also benefited from the fact that no one in the current field has the ability to capi­tal­ize on the weaknesses we listed above.

The key date in setting Romney’s course in the primary contest may have in fact then been May 14 — the day former Arkansas governor Mike Huckabee decided not to run.

At the time, Huckabee’s decision was greeted without much surprise by the political class. After all, he had shown no willingness to raise money or build the sort of early state organizations that conventional wisdom suggested he would need to compete with Romney.

But, a look at how the race has played out since then suggests it was tailor-made for Huckabee.

First, the entire dynamic of the contest was driven by the myriad debates held over the summer and fall of 2011, debates in which Huckabee — if his 2008 performances were any indication — would have shined.

Huckabee’s inability/unwillingness to raise money or create a traditional organization would also have mattered far less than we all thought a year ago. Huckabee was at or near the top of every national poll when he decided not to run, a coveted position that would have put him front and center in every debate — and virtually ensured significant free media coverage in the wake of the gatherings.

Second, Iowa became a total free-for-all once Huckabee, who had won the caucuses in 2008, stepped aside. No candidate was able to put together the social conservative coalition that Huckabee would have had from the second he announced his candidacy.

With Huckabee in the race, there’s no chance that Romney plays in Iowa aggressively and an even smaller chance that the former Massachusetts governor win the caucuses.

Without an Iowa win, a Romney victory in New Hampshire is less monumental and South Carolina shapes up as a showdown between Romney and Huckabee. (It’s hard to imagine former Pennsylvania senator Rick Santorum or former House Speaker Newt Gingrich still in the race in South Carolina if Huckabee is running and uniting conservatives behind his cause.)

Third, Huckabee is not only an evangelical Protestant but he’s also a former preacher. He is regarded by religious Republican voters as one of them — someone who isn’t just catering to them because it’s good politics but rather someone who understands at a basic level what they care about.

While Santorum and Gingrich are both making that same pitch to evangelicals, both men are Catholics. Huckabee wouldn’t have even had to court that critical voting bloc. They would have just been with him.

Fourth, and perhaps most importantly, Huckabee is the economic populist that this field badly lacks.

There is clearly an effective attack to be made against Romney as someone who is out of touch with the average person. But no one in the current field can effectively make it.

Gingrich is of considerable means himself and is not even close to a populist. Santorum has potential but seems more focused on winning over social conservatives than turning himself into a populist. Texas Gov. Rick Perry should be the economic populist in the race but his inability to articulate any message at all has made that impossible.

Huckabee’s natural folksiness oozes populism as, it’s worth nothing, do his struggles with his own weight. Can you imagine what Huckabee would have done if Romney tried to make a $10,000 bet with him during a debate?

Obviously, hindsight is 20-20 and it’s not clear that if Huckabee had run, the race would have played out as it has over the past year. It’s also worth noting that Huckabee had a number of weaknesses — his spending and tax record in Arkansas for one — that would have come under withering scrutiny from the Romney team.

Still, there’s little question in our mind that had Huckabee run, he would have presented — by far — the most difficult hurdle to Romney’s chances of winning the Republican nomination.

He didn’t. And the rest is history.