The Democratic Party may be able to put a national ban on fracking, but only if it gets a democratic president. Congress, while composed of many republicans, could advance the cause as republicans have shown no willingness to fight for its constituents. A ban on fracking is just a matter of time.
I wouldn't expect the Democratic Party to put a nationwide ban on fracking in the platform although it could adopt language to phase out fracking. Fracking now accounts for two-thirds of natural gas and natural gas accounts for one-third of electricity. Unless the public is willing to live with rolling brownouts and blackouts or a tremendous increase in coal burning fracking will have to continue for awhile. It should be phased out as solar, wind, and geothermal are phased in. Everyone in the US needs electricity and much of the population needs heating. These needs cannot be ignored by a major political party. You can't have the Republicans saying we will provide you with electricity and the Democrats won't.
A fracking ban will not be politically viable until there is a sustainable energy movement that can cover home heating and transportation. There are too many big businesses dependent on the practice at the current time. The party needs to develop alternative energy answers before a permanent fracking ban will be viable.
Fracking is so widespread and is such a vast monetary industry that even if they successfully banned it nationally, it wouldn't just stop. People would do it anyway, because as of this time, not doing it would be poor for the economy. It would lessen it probably, but it's unlikely to be banned at all with so many people against it.