In many cases, internal links are often undesirable things by themselves, and could be considered impacts. However, the worst of the consequences, or the final one in the chain of events, is usually given the label of "impact". For example, nuclear war is probably worse than economic collapse, so nuclear war is given the "impact" label, even though economic collapse (the internal link) could itself be viewed as an impact.
The nuclear war impact is the terminal (i.e. final) impact in virtually every disadvantage today. While it appears outlandish to outsiders and even debaters now, it originated in the 1980s during the height of the nuclear freeze movement, specifically after the publication of The Fate of the Earth by Jonathan Schell. Barring nuclear war, the terminal impact usually ends up as extinction anyway, either human extinction or the extinction of all life on Earth; the most common mechanisms for these are cataclysmic climatic change (in the style of The Day After Tomorrow) and all-consuming conventional war.
Other terminal impacts might include severe human rights abuses, such as near universal slavery. These types of impacts are usually argued under a deontological framework or as a turn to a human rights advantage.
Non-kritikal linear disadvantages frequently face attacks from the Affirmative on debate theory; the theory that linear disadvantages are abusive (i.e. unfair) to the affirmative team has such widespread acceptance in the world of debate that the linear disadvantage has become especially rare.
A variant of the Politics disadvandage is the Elections disadvantage, which is run during either Presidential or Midterm elections cycles. For example, in a presidential election, it might argue that a certain Presidential candidate or his or her opponent is currently weak (or strong), but the affirmative plan will cause him or her to gain (or lose) popularity, and that either his or her election is undesirable or the election of his or her opponent is undesirable. A midterms version could focus on particular races or the general balance of the Congress; an example of a single-race midterms disadvantage would be that the reelection of Senator Daniel Akaka is critical to free speech, and plan prevents Akaka from winning; a "balance of Congress" disadvantage might hold that the plan is a credit to the Republicans, who would increase their grip on Congress and allow extensive drilling in the Arctic National Wildlife Refuge.
Other debate theorists have recently created a model of fiat that appears to preclude the politics disadvantage; however, its use in any given debate round is entirely dependent on how well the affirmative argues that the judge should accept the model, a somewhat time-consuming process.
Tradeoff DA - plan takes $ from more important things
Economy/Spending DA - plan leads to economy collapse/recession
Federalism DA - aka the "fism DA" - says that plan = undermine federalism (balance of powers between USFG and states), and since most countries model their democracy on the US, if the US destroys their federalism, then wars will break out in other countries as a result
Constitutionality DA - plan = unconstitutional, and creating it would set a bad precedent, causing other unconstitutional policies to be passed
Overpopulation or "Malthus DA" DA - By the plan saving lives, it undermines natural death checks, which lead to overpopulation and a "Malthusian" catastrophe because of it
By reading evidence that says the impacts will occur regardless of plan passage, the links and impacts (and thus the entire disadvantage) become largely irrelevant.
No Link: The plan expends no political capital
Using the example above, an a no-internal-link could either be that the failure to pass the deal will not reduce American influence on the Indian subcontinent, or that reduction of American influence on the Indian subcontinent will not lead to nuclear war between India and Pakistan.
Uniqueness: US Military Strong
Link: Plan Decreases military power
Impact: Weak military leads to nuclear conflict.
A non-unique and a link turn would go something like this:
Non-unique: Military weak now.
Link Turn: Plan increases military power.
This strategy turns what was previously a "disadvantage" to the plan into a benefit or advantage of the plan.
Another way to debate against a disadvantage is an impact turn, in which the affirmative team reads evidence stating that the disadvantages impact would actually be good. If the impact to a disad was global nuclear war, an impact turn would say that death is good. Often impact turns function at the level above this. The argument is then sometimes called an internal link turn. For example, if the disadvantage argued that the plan hurt free trade, which was key to avoiding war, the affirmative might argue that in fact free trade caused war, environmental destruction, and other negative consequences. This type of turn is often much harder to convince the judge of (in part because of the structure of a debate round, in particular, the negative block), but some believe that it makes a round much more interesting.
In answering the Link, an affirmative might argue that the link has no threshold, i.e. that the link does not make clear the level of a particular type of action that will cause the impact, or that uniqueness overwhelms the link; that conditions in the status quo are so far away from the threshold that the impact will not happen. This second answer is rarely made however, because it is a strategic gamble.
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