Which group is most likely to display a consistently liberal or consistently conservative ideology?
This is a somewhat difficult question to answer because different people will define conservatism and liberalism in different ways.
On the one hand, we know that African Americans are the group that is most likely to vote for Democrats while white, evangelical Christians are most likely to vote for Republicans. But this does not mean that these groups are necessarily consistent in their liberalism or conservatism. African Americans, for example, tend to oppose gay rights. Many evangelical Christians do not believe in conservative dogmas such as the need for free trade.
The group that is most likely to be consistently liberal is highly educated people who live in cities and are not religious. These people are liberal on both social issues (they tend to support abortion rights and gay marriage) and on economic issues (they support government regulation of the economy and government programs to provide a “safety net”).
It is very difficult to identify a group that is consistently conservative. This is because conservatives believe in laissez-faire economics and free trade along with traditional moral values. It is hard to find a definable group that consistently believes in both of these things.