The core concept here is understanding the Democrats' belief about the voting behavior of the younger generation. The correct answer is based on the information that Democrats believe young voters will turn out at higher rates and replace older generations, ensuring continued victories for the Democratic party. Option A is incorrect because it suggests a shift to the Republican party, which is not mentioned. Option C is wrong because it implies a delay in voting until having children, which is not the Democrats' belief. Option D is incorrect because it suggests a permanent liberal stance, which is not the focus of the Democrats' prediction.