Bush won with 51% of the votes. 44.66% (58% of 77%) of the vote on that day were by whites for Bush. 44.66/51= 87.57% of Bush's votes came from whites. As to Christianity, 45.9% of all people who voted were Christians voting for Bush (59%*54% + 52%*27%). 45.9%/51%=90%
Your link doesn't have enough information (percentage of adherents of a religion that is one race or another), but since 87.5% of Bush's votes came from whites, and 90% of his votes came from Christians. At a minimum, 76.5% of his votes would have come from White Christians. That seems like a supermajority to me. For democrats, the figure is most likely a majority, but not nearly as much as for Republicans. In fact, let me calculate it.
42%*77%=32.34. 32.34/48=67.375% of Democrats are white.
40%*54%=21.6%. 47%*27%=12.69. 21.6+12.69=34.29. 34.29/48=71.4375% of Democrats that are Christians.
At a minimum, 41.75% of Democrats are white Christians. Using minimums only, a minority of Democrats are white Christians, whereas a supermajority (75% even, in this case) are white Christians in the Republican party.
Evangelicals aren't the only Christians.