WASHINGTON (WASHINGTON POST) - It took a historic tie-breaking vote cast by US Vice-President Mike Pence on Tuesday (Feb 7) to get President Donald Trump's education secretary nominee Betsy DeVos confirmed by the Senate.

A few months ago, very few people would have predicted she would be confirmed on a 51-50 vote, the narrowest confirmation vote of a Cabinet nominee ever. Two Republican Senators Lisa Murkowski and Susan Collins joined the entire Democratic caucus to oppose her.

But in retrospect, what happened to Mrs DeVos makes sense. Her inexperience in public schools, her alienation of some moderate Republicans, a powerful populist movement against her and Senate Democrats' will to oppose Mr Trump at every turn came together to create the perfect storm.

There are several dynamics going on and here's a breakdown of them into four factors:

1. She's a one-issue nominee

Mrs DeVos, a Michigan billionaire philanthropist, is a national figure on the cause of giving vouchers to parents so they can choose whether to send their kids to private or public schools. That is mostly a non-starter for Democrats. But the school-choice-above-all-else narrative also doesn't fit with some red-state Republican senators, whose rural states don't necessarily have a tonne of private or charter schools to choose from.

"If you are a senator who disagrees with DeVos on the issue of school choice and vouchers, there aren't a lot of other places to find common ground," said Ms Elizabeth Mann of the Brookings Institution.

2. She doesn't have experience in public schools

Mrs DeVos has not attended, sent her children to, or worked in public schools. And that's a big problem for people who see the education secretary's primary role as managing public schools, which a majority of American students attend.

"(L)ike all of us, Mrs DeVos is the product of her experience," Senator Collins said on the Senate floor explaining why she'd be voting against Mrs DeVos.

Mrs DeVos' viral confirmation hearing - where she seemed unfamiliar with basic laws and suggested guns in schools could help protect students "from potential grizzlies" - did nothing to assuage those concerns. And it even added a few more, like whether she'd support students with disabilities.

3. A united opposition, a split front of support

The increasingly nationalised debate over school reform has propped up a sizable, well-organised and often powerful coalition of labour and progressive groups that are opposed to Mrs DeVos' school choice position.

But it's not just teachers unions opposing her. The Washington Post talked to parents across the country who opposed Mrs Devos and found them to be part of a surprisingly diverse group:"(A) small army of parents, teachers and others around the country who have risen up against DeVos as President Trump's nominee heads toward a breathtakingly close confirmation vote. They come from places as diverse as rural Alaska, inner-city Detroit and … suburban Nashville."

"Vouchers don't come with any oversight of the schools in which they're spent," Ms Anna Caudill, a Tennessee mother of two, said.

Very few Cabinet nominees have such a built-in and well-organised opposition, said Mr Frederick Hess, a DeVos supporter with the American Enterprise Institute. "I don't know who has that kind of mobilisation on the secretary of state, no matter how much more high-profile the position is," he added.

4. Senate Democrats are at war with Mr Trump

Senate Democrats' unanimous opposition to Mrs DeVos is rare. For decades, the Senate's practice has been to give new presidents deference in their Cabinet picks. But nothing about Mr Trump's presidency is normal, and Senate Democrats are making his picks go through extraordinarily high hurdles to get approved.

Secretary of State Rex Tillerson was the first secretary of state nominee in US history to ever have to clear various procedural hurdles before a final confirmation vote.

Democratic senators have boycotted committee votes on Mr Trump's nominees for treasury, the Environmental Protection Agency, and health and human services, forcing Republicans to suspend the rules and advance the nominees without a quorum.

Mrs DeVos, for all the reasons listed above, provided Democrats the perfect opportunity to take their biggest stand yet against Mr Trump.

In the end, she got confirmed, but Democrats succeeded in making it one of the most contentious battles to date for a Cabinet nominee.