Snowballing -2 lemma

The snowballing -2 lemma states that in MediaWiki, then it's immediately certain that the change will eventually receive a +2.
 * given a proposed change with uncertain consensus,
 * if a -2 is placed over the change to prevent its merge,

The interim name of the lemma derives from the Snowball clause: a -2, in fact, declares in advance of closure that there is a consensus for merge. Otherwise, there would be no need to try to prevent the merge with force.