President Trump issued an executive order on Thursday October 12th allowing people to buy cheaper, less comprehensive insurance plans than those offered on the ACA marketplaces. Because it could prompt some healthy consumers to drop their marketplace plans, which would alter the overall risk pool, experts characterize this as one of many efforts by the Trump administration to undermine the 2010 health care law.

Here are points in the process the administration has affected the marketplace's operation so far:

1. Insurers and states prepare for the beginning of open enrollment

Insurers have to get their plans approved by the exchanges, and sometimes by state regulators. At the same time, states have to prepare for the open enrollment period which starts Nov. 1.

ROADBLOCK: Trump hasn't said whether he will continue to fund key subsidies

It's difficult for insurers to know how to price their plans because the Trump administration has not committed to paying cost-sharing reductions, subsidies that help offset low-income Americans' deductibles and co-pays. Insurers in most states have raised their 2018 premiums significantly to account for the fact that it's unclear whether the government will pay the billions in cost-sharing payments next year.

ROADBLOCK: Trump might not strictly enforce ACA's mandate to buy insurance

Whether federal officials strictly enforce the individual mandate, which requires taxpayers to provide proof of health care coverage, also affects insurers' pricing. The more it's enforced, the more likely it is healthy people will enroll, which in turn lowers insurers' costs and what they charge for premiums.

ROADBLOCK: HHS is not helping states plan for enrollment season

Every year, the Department of Health and Human Services has sent regional directors to help states get up and running for open enrollment. This year, they're not coming.

2. People learn about open enrollment.

People need to learn that the marketplace exists, whether they'll eligible for Medicaid or subsidies, and how to enroll.

ROADBLOCK: Trump has slashed the ACA advertising budget

The administration announced it would spend $10 million on advertising open enrollment, one-tenth what the Obama administration spent last year. That could mean fewer people will hear about the enrollment period.

ROADBLOCK: He also cut funding for ACA 'navigator' groups

ACA navigators tell people in their community about the open enrollment period and help them sign up for the exchanges. The Health and Human Services Department is slashing the navigator budget by 40 percent overall, up to 92 percent in some places. Some navigator organizations have already shut down as a result.

3. People decide whether they want to enroll.

The decision is based on whether people think the marketplaces are functional and offering them good plans, as well as whether they think they'll be punished under the individual mandate.

ROADBLOCK: HHS has put out negative advertising about the marketplaces.

The Trump administration has advertised against the ACA. By emphasizing messages that the market is imploding or the plans are too costly, the administration has discouraged people from enrolling.

ROADBLOCK: Trump might not strictly enforce ACA's mandate to buy insurance

Insurers aren't the only ones impacted by the lack of information on the enforcement of the individual mandate. If the enforcement looks like it will be lax, many people may opt to not enroll in the marketplace.

ROADBLOCK: Trump is allowing people to join "association health plans" instead

These plans would allow people to buy cheaper, less comprehensive insurance than is offered in the ACA marketplaces. Experts expect it to pull healthy people out of the marketplaces, increasing average costs and therefore premiums.

4. People go through the enrollment process.

The process can be confusing and involved, so it can take people a while to get from first learning about the marketplace to completing their sign-up.

ROADBLOCK: The administration cut the open enrollment period in half

The open enrollment period, when people are able to sign up for the exchanges, used to span from Nov. 1 to Jan. 31. The Trump administration cut this in half, ending the period on Dec. 15. A spokesperson for HHS said this is because Obamacare missed its enrollment targets in the past. And beyond that, Healthcare.gov is being shut down for several hours most Sundays. Since people have less time to enroll, it's likely that fewer people will get the message in time.

ROADBLOCK: The shorter enrollment will also put more strain on Healthcare.gov

As it stands, Healthcare.gov has a hard time handling the surge of traffic in mid-December (so people can get insurance starting in the new year) and the end of January (so people can make the deadline). By changing the open enrollment period, these two surges will occur simultaneously in mid-December, according to Karen Pollitz of the Kaiser Family Foundation. Since there's no signs the technology will be upgraded, this could cause the website to crash.

Kevin Uhrmacher contributed to this report.