So is it Donald Trump or Ben Carson? The property developer or the pediatric surgeon?
Recent polls show Mr Carson taking first place among Republicans nationwide and consolidating a growing lead in Iowa. A different poll, however, shows Mr Trump’s lead surging nationally, with Mr Carson in second place.
Either way, the race is remarkably stable. The two outsiders continue to take roughly half of the Republican field between them, leaving the other 14 candidates to fight over the scraps.
Moreover, normally cautious Republican figures now say that one of the two could actually win their party’s nomination. Until a few weeks ago, wise heads shook reassuringly at that prospect. Many of those same people now see a Trump or Carson nomination as a probability.
Can the end of Republican days be far off?
The question is only partly tongue in cheek. As Mr Carson has begun to challenge Mr Trump’s lead, the latter has increasingly targeted him for special treatment.
That has included highlighting Mr Carson’s faith — his membership of the obscurantist Seventh-day Adventist Church. Mr Carson has repeatedly avowed his faith in all the Adventist church’s tenets, including the belief that humanity’s “end of days” is imminent.
Some have even taken that to explain why Mr Carson is so relaxed about climate change. Why bother with the future if history’s reckoning is round the corner?
Mr Carson’s faith, and Mr Trump’s evident lack of piety, explain the former’s solid popularity in Iowa. According to surveys, more than a third of registered Iowa Republicans are born-again evangelicals.
New Hampshire is a different matter. Its Republican party tends to be more libertarian. The “Presbyterian” Mr Trump is still in the lead there.
But these are details. As the Republicans limber up for their third prime time debate on Wednesday evening, the rivalry that will rivet most viewers is between the only two men on stage who have never held elected office.
Opinion polls can no longer be dismissed as fleeting moods. Mr Trump has led the Republican field now for almost 130 days. It is all too easy to imagine him sustaining that lead in the remaining 96 days before the Iowa caucus.
Almost the same applies to Mr Carson, who has stayed in second place — and now first, according to one poll — for most of the past three months.
No other candidate, including Marco Rubio, the Florida senator, who many now see as the establishment’s only viable choice, has managed to sustain a showing in double digits…