Razib Khan has some truly excellent analysis of why Asians vote Democratic:
Barry Kosmin has documented that between 1990 and 2010 Asian Americans have become far less Christian , on average. Meanwhile, the Republican party has become far more Christian in terms of its identity. Do you really require more than two sentences to infer from this what the outcome will be in terms of how Asian Americans will vote?
Razib backs this up with solid quantitative analysis. He shows that Asians are just as Republican as non-Asians after factoring in religion. For example, evangelical Asians are 56% Republican compared to only 50% of non-Asian evangelicals. The problem for Republicans is that Asians are only 42% Christian (of all denominations). The Republican Party’s close association with evangelical Christianity is a huge turnoff to non-Christian Americans.