Final answer:
The sentence structure error is in the sentence about Democrats' and Republicans' ideas.
Step-by-step explanation:
The group of words containing a sentence structure error in the given sentence is The Democrats never seem to have any good ideas, the Republicans always have really good ideas. The error is the lack of a coordinating conjunction (such as 'but' or 'and') between the two independent clauses. To fix this error, the sentence could be rewritten as 'The Democrats never seem to have any good ideas, but the Republicans always have really good ideas.'
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