I believe that effective sanctions would be the only catalyst needed for regime change. Give a 2 month grace period, then impose extra duties of 3% on imports to the USA from any country buying Iranian oil. The Chinese, Indians, Japanese and Koreans would sever ties with Iran quickly, and the mullahs would lose their grip inside a year. The Chinese have already started to reduce their US treasury bill holdings and allowed the currency peg to loosen. The Chinese won't buy more Treasuries to retaliate... US voters would love to see Obama show some backbone on this front.....rather than confronting China on this Rare Earth materials nonsense.
Hungary's Orban: Refugees threaten Europe's Christian roots (Reuters)
from the article: Iranian activist says regime change could resolve nuclear standoff