Jeb Bush in Peterborough, N.H., last week. (Brian Snyder/Reuters)

What happens when a candidate whose greatest strength is the sense of inevitability surrounding him becomes something short of inevitable?

That’s the question that is facing former Florida governor Jeb Bush’s presidential candidacy amid only so-so polling numbers nationally and in early-voting states and that is behind a fundraising operation premised on “shock and awe” but is, to date, producing mostly “awww.”

Bush’s campaign was built to look a lot like his older brother’s successful bid for the White House in 2000. Huge amounts of fundraising and the best staff money can buy, sprinkled with establishment blessings — mostly in the form of endorsements — were deemed necessary.

But it has become quite clear over the past few months that not only is Jeb Bush not George W. but that the GOP of 2015 is not the Republican Party of 2000.

Republican presidential candidate Jeb Bush calls out Donald Trump on his lack of military experience and weak foreign policy in a video released Saturday, Oct. 17. (Jeb Bush)

Jeb Bush is soft-spoken and sort of nerdy by nature. (As a fellow nerd, I recognize my own kind.) He has few sharp edges, whether in personality or policy. His brother, by contrast, was the cool kid everyone wanted to hang out with — and whose natural tendencies in public life positioned him on the more-conservative end of the spectrum.

Jeb Bush’s demeanor has turned out to be a poor fit for a Republican Party — and, more specifically, a Republican base — that wants confrontation at all times and on all fronts.

The Republican front-runner and reality TV star Donald Trump carries himself like a grade-school bully — all strength, bluster and hair. Trump calls anyone who dares to oppose him a classless loser who doesn’t know what it takes to make America great again.

In the face of that sort of onslaught — Trump’s latest broadside against the Bushes is the oblique suggestion that George W. Bush may bear some responsibility for the terrorist attacks of Sept. 11, 2001 — has left Jeb Bush flummoxed. You can almost see the “I can’t believe I’m losing to this guy” thought hanging over his head at all times on the campaign trail.

But what about the structural advantages Bush has? you cry. And, yes, he has some. But money, which was long assumed to be his massive and most important edge in this race, has turned out to be less impressive and less determinative than anyone had thought.

Bush has raised just over $13 million during the past three months and has collected $25.8 million for his campaign committee this year. By comparison, Hillary Rodham Clinton, the Jeb Bush of the Democratic presidential race, collected $28 million over the summer and has raised $76.5 million total for the contest. George W. Bush? He had raised about $57 million for his candidate committee by the same time in 1999.

Jeb Bush, of course, has long been given a pass on his candidate fundraising because his super PAC — Right to Rise — brought in more than $100 million over the first six months of the year, an unprecedented haul.

But his big bet on his super PAC hasn’t paid off yet. Right to Rise has spent more than $13 million on TV and online ads in support of Bush’s candidacy in early states and seen almost no results. He is in fifth place in New Hampshire and sixth place in Iowa, according to the Real Clear Politics polling average in the two states that will kick off the 2016 primary season.

And evidence is growing that a well-funded super PAC can’t save a candidacy. Rick Perry and Scott Walker struggled to raise money through their candidate committees and were eventually forced from the race, despite aligned super PACs that were sitting on millions of dollars.

Of course, Right to Rise will continue to spend; it has booked $17 million worth of TV advertising in states that have primaries or caucuses in March, when more than 50 percent of all GOP delegates will be allocated. No other candidate this side of the purportedly self-funding Trump will be able to keep up with that pace.

But the question that has to haunt Bush and Right to Rise — and the rest of the party establishment that lined up behind this “juggernaut” months ago — is this: What if the dog just doesn’t like the dog food?

As in, what if — no matter how many TV ads Right to Rise runs, no matter how many endorsers support Bush, no matter how good his staff is — Republican voters just don’t want to vote for him? That question has been made all the more scary as any lingering remnants of Bush-as-the-inevitable-nominee have washed away, exposing him for what he is as of now: a candidate who has yet to demonstrate any real appeal to GOP voters either nationally or in key early states and who, by the way, isn’t the fundraising behemoth everyone thought he would be.

What Bush needs to find — and fast — is a compelling reason why undecided Republicans need to be on his side. Without that, all the money, endorsements and last-name credibility in the world won’t win him the GOP nomination next year.