  We study the dynamics of electroweak symmetry-breaking in an extension of the
Standard Model where the Higgs sector is augmented by the addition of a real (Y
= 0) isospin triplet. We show that this scenario exhibits a novel, two-step
electroweak phase transition, wherein the first step provides the strongly
first order transition as required for electroweak baryogenesis followed by a
second step to the Standard Model Higgs phase that also admits a cold dark
matter candidate. We analyze the constraints on this scenario from recent
results obtained at the Large Hadron Collider for the Higgs diphoton decay
channel. We argue that this two-step scenario can be generalized to extensions
of the Standard Model with additional higher-dimensional scalar multiplets that
may yield realistic baryogenesis dynamics.
