Medicaid was created by the federal government, but the federal government relies on the various states to implement its provisions. Those states, in turn, are given some flexibility in the way they go about implementing the Medicaid program. Thus, the experience that someone has - say - in New Hampshire, might be different than the experience that someone has in Abilene, Texas, where I practice.
Under the federal law, the states are required to provide retroactive benefits for Medicaid coverage during the three-month period that immediately proceeds the application process. However, the federal Medicaid program also allows for states to apply for "waivers" - which could potentially eliminate the 3 month requirement.
Recently, there has been a trend where states apply for a waiver that eliminates the 3 month requirement. Arizona, Florida, Iowa, Indiana, Massachusetts, Rhode Island, and Tennessee all have programs that eliminate retroactive coverage. Delaware, Hawaii, and New Mexico have also eliminated retroactive coverage, but their particular waivers don't apply to people who are institutionalized. Three more states - Arkansas, Kentucky, and New Hampshire - are also asking for elimination of the 3 month requirement, but their requests for waivers are currently held up in litigation.
So far, there has been no indication that Texas will apply for a waiver - which is a good thing. Nonetheless, I am recommending to all of my potential clients that - if they think they may need to get on Medicaid at some point in the future in order to avoid going completely broke as a result of paying for long-term care - it is better to start planning right now to make sure you are ready. It is possible for things to change very, very quickly in today's political environment, and you don't want to end up being responsible for unnecessary medical debt.