  Models with scalar triplets can have a large impact on the electroweak
precision S-parameter and have to be dealt "with extreme prejudice". Such
models, and in particular the Georgi-Machacek (GM) model, involve a complex
triplet scalar containing doubly-charged Higgses plus a real triplet and are of
recent phenomenological interests. It turns out that large mass splittings
within the triplet will not be allowed by the S-parameter in the absence of
extra fermionic degrees of freedom. Simply speaking, having only an extra
triplet of scalars severely restricts the mass splitting within that triplet
even with the present precision on the S-parameter which will further be
improved with the proposed Higgs factories.
