When a few million people stood to lose insurance that they liked under former President Barack Obama's healthcare law, it created one of the biggest political crises of his presidency. Now five years later, Sen. Kamala Harris, D-Calif., a leading presidential candidate, is openly calling for getting rid of private insurance, which currently covers 177 million people. Have politics changed that drastically in just a half of a decade?

Harris made the comments during a CNN town hall style interview in response to a question from Jake Tapper, who pressed her on what her support for national healthcare, which she describes as "Medicare for all," would mean for those who had private insurance that they liked.

"Listen, the idea is that everyone gets access to medical care and you don't have to go through the process of going through an insurance company, having them give you approval, going through all the paperwork, all of the delay that may require," Harris said. "Who of all us have not had that situation where you have to wait for approval and the doctor says, 'I don't know if your insurance company is going to cover this?'"

She continued, "Let’s eliminate all of that. Let’s move on.”

But an effort to "move on" from private insurance would be tremendously disruptive. In 2017, the most recent year for which data are available, there were 156.2 million people who obtained private insurance through their employers, and 20.5 million who had it directly through insurance companies, according to the Kaiser Family Foundation.

[Related: Howard Schultz: Kamala Harris’ call to ban private health insurance ‘not American’]

Furthermore, Americans with private coverage by and large like it. According to Gallup data, 70 percent of those with private insurance rate their coverage as "excellent" or "good," and 85 percent say the same about the actual healthcare they receive.

Harris would be throwing more than half the country off of plans they're currently comfortable with in exchange for a promise of a great new hassle-free government plan that doesn't exist yet.

Indeed, a recent Kaiser survey that found 56 percent support for a national healthcare plan described as "Medicare for all," but that support drops to 37 percent when told such a plan would "eliminate private insurance companies," with 58 percent opposed.

This doesn't even take into account the other tradeoffs involved with converting to the system she's calling for. For instance, the staggering taxes that would have to be levied not just on the uber rich but also on the middle class; the massive layoffs that would result from putting a major industry out of business; the access problems that result when you're giving everybody "free" healthcare while putting downward pressure on payment rates to doctors, hospitals, and other medical providers.

The shortcomings of Obamacare, the bungled Republican repeal efforts, and the mind-bending presidency of Donald Trump have all made ambitious Democrats such as Harris believe that the ground has fundamentally shifted in politics. Equivocating about how her socialized health insurance plan won't really threaten private insurance will only open her up to attacks of dishonesty. If she's direct about it, she comes across as confident and bold, she'll be on good terms with her base, and she assumes, it will not actually cost her a general election race against Trump.

It's quite possible that this calculation proves to be true in a 2020 election that's likely to be chaotic. But as I wrote recently, there's a big gap between promises made during an election and what can actually be achieved in office. Voters may glaze over policy details during a campaign, but once something migrates from an abstract campaign position into a possible law that could have a dramatic effect on people's lives, they start paying attention, and that could mean significant defeat once in office. Harris has obviously determined that this is worth the gamble.