Easily 2004. In 1988, the US really was a center-right country. But it was realigned in the 90s. There's a reason why 2004 is the only time a GOP president has won the popular vote since then, and even then by just 2.5 points. The electorate of 2004 was just far more liberal than 1988.
ehh the nation realigned in 2008, the nation was a very conservative country from 1980-2008(relatively of course).
Democrats had to run away from the word liberal and you a Democratic President embrace Welfare Reform, Deregulation, Tough on Crime policies, capital gains tax cuts