Where his rivals once expected him to flame out before the first vote was cast next year, the consensus among the nearly two dozen campaign staffers and GOP operatives interviewed for this story is that he’ll be a force long past the Iowa caucuses on Feb. 1. The old theory of the case – that the nomination would ultimately narrow down to Bush and one other candidate – is out the window…

Yet Bush isn’t the only rival whose fortunes have notably changed in just a few months. When the summer began, Scott Walker looked like a safe bet to win the Iowa caucuses next year. Now, an overly scripted style and inconsistencies on key issues have led him to plummet to fourth in the polls there and raised questions about his staying power. Rand Paul, seen just a year ago as the most viable anti-establishment Republican in the field, is now an afterthought, relegated to a smaller map where his libertarian stylings might still have appeal.

One candidate, in particular, has thrived: Ben Carson, the retired pediatric neurosurgeon once thought to be the longest of long-shots. An outsider like Trump, Carson has surged into second place in national polls in part by riding in Trump’s slipstream, finding success by picking up Christian conservatives who are angry at the GOP establishment but turned off by Trump’s bombast and ostentatious style.

While Walker and Paul’s woes can’t be directly traced to Trump’s entry into the race, the environment he’s helped create makes it that much harder for faltering candidates to break through and regain their footing – the billionaire is chewing through news cycles, and leaves limited oxygen for anyone else.