Where to begin? It's been a hectic day, but I'll sure try: So, when the ACA was being introduced in 2008-2009 or so, the bill proposals that featured a public option lost out in the House. Now, no public option was a big deal at the time, because there would have been significant cost savings associated with it. One of the major benefits of the ACA that was being touted at the time, and one of the roadblocks put up by moderate Democrats, was that the legislation had to save money. The CBO checks it out, writes up a pretty report objectively analyzing the savings from the bill, and it becomes even easier to pass.
With the cost savings of the bill in jeopardy, Pelosi had to look at other ways of saving money. This is about where our story begins, because Pelosi and other heavy hitters in the House came up with the idea of expanding Medicaid requirements so that they could be shunted onto that program instead.
http://swampland.time.com/2009/10/29/medicaid-the-other-public-option/
Once the Speaker decided to go with the weaker version of the >public option, she found herself with another problem. Because the >weaker version saved less money, she would have to find $85 >billion, so the bill’s 10-year price tag could come in under the >$900-billion limit that President Obama had set. One way to do >that was to take 2.5 million people who would have been using >government subisidies to buy insurance on the new “exchanges” >that would be established under the bill, and shift them instead >into the Medicaid program. So instead of setting the qualifications >for Medicaid at 133% of poverty, as the legislation initially >stipulated, the level was lifted to 150%. (In other words, where a >family of four earning up to about $29,300 would have qualified for >Medicaid under the initial version of the bill, the program now >would accept a family earning up to about $33,000 a year).
The number they're using for the poverty line is a little low, but if we adjust it for 2015 figures using their 150%, it now comes out to about $37,000 a year as the Medicaid cutoff, for a household of 4.
The reason is because, you see what we're doing here, we were trying to keep the bill fiscally sound, but also more people who didn't used to qualify for Medicaid started to qualify for Medicaid. This is the so-called Medicaid expansion from the bill, that the Supreme Court struck down and made only optional for states that wanted to opt in. It was vehemently fought by Republicans, because as the poverty gap widens and the topmost income that still qualifies for Medicaid is raised, you're suddenly looking at an increasingly growing chunk of the U.S. population--a chunk of the population that effectively has a health care public option. It's a slippery slope argument, sure, but what would stop a new bill from making the percentage 160%...170%...300%...1000% of the poverty limit, for us all to qualify for Medicaid? Suddenly a social safety net for the poor becomes a primary health insurer of the entire middle class. It's sneaky, and is thought of in Republican circles as a "backdoor" to the public option.