1. Mandatory spending is created when a law has the appropriation for the cost of the law
included in the law itself.
2. Discretionary spending occurs as a result of a law being passed that authorizes spending for its cost,
but doesn't appropriate that spending. The appropriation has to occur via other, separate legislation.
(Feel free to tell me where I'm wrong about that before I make my point related to it.)
So, without objection, here's my point:
1. The House Republicans could not get the votes to defund Obamacare because it is funded in the law itself, and thus the law itself had to be changed in order to effect such defunding.
In short, they lost that legislative battle. However,
2. ...the House Republicans could effectively defund unrelated discretionary programs, because they require an affirmative legislative action periodically to get their funding,
and all the House Republicans had to do was
not act to fund them.
That is how, figuratively speaking, the hostage taking occurred. Discretionary spending, unrelated to Obamacare, could be held hostage, simply by inaction,
in what the House Republicans believed was a good scheme to overturn the results of the battle they lost in 1 above.
3. What they did was not illegal, technically, but it was slimy, sleazy, and weasely, and as public opinion has borne out,
it was not a good plan, because not everything that is technically legal fares well in the court of the People,
and we still are, at least theoretically, a government of the People.
In short, the GOP House members tried to game the system, and they lost. At least it appears at this point that they lost.