In 2005, Romney revealed a change of view regarding abortion, moving from the abortion rights positions expressed during his 1994 and 2002 campaigns to an anti-abortion one in opposition to "Roe v. Wade". Romney attributed his conversion to an interaction with Harvard University biologist Douglas Melton, an expert on embryonic stem cell biology, although Melton vehemently disputed Romney's recollection of their conversation. Romney subsequently vetoed a bill on pro-life grounds that expanded access to emergency contraception in hospitals and pharmacies (the legislature overrode the veto). He also amended his position on embryonic stem cell research itself.