An example of how the Democrats could have taken to rhetorical high ground: they could have countered Boehner's references to our weak recovery as "the Obama economy", and his placing the blame for our economic weakness on "President Obama's policies", by aggressively turning the blame for the slow recovery back onto Boehner himself.
What I would have liked to hear: it was President Obama's stimulus policy that pulled us back from the brink of a more severe depression in 2009, and led to the recovery here in the US that has done better than most of the other industrialized countries. We can call that period of 2009-2011 the "Obama economy." But when it was apparent that the slow recovery needed more stimulus, Mr. Boehner and his party refused to pass the bills requested by the president to boost the economy, begin repairing our crumbling infrastructure, and create millions more jobs. A clear dichotomy: President Obama's policy of stimulating the economy for faster growth, John Boehner's policy of obstruction for the sake of obstruction, resulting in continuing slow growth. So we can call the struggling economy "the weak Boehner economy" - and after you've undercut the president's policy, how dare you refer to the "weak Boehner economy" as the "Obama economy"!
Another example: when the Republican governors refused to set up the state exchanges anticipated under the ACA, it was evident that they were acting out of political spite, to the detriment of the people of their states. And much of the obstruction in congress has also been purely out of political spite, not based on the merits of legislation or appointments. I would have liked to have seen the Democrats jump on the phrase "political spite", and hang it (justifiably) around the necks of the Republicans - let them be on the defensive, and try to show that they were not acting out of spite.
There are plenty of other issues on which the Democrats could have put the Republican on the defensive. I think that the example of these two memes - "the weak Boehner economy" and "political spite" could have helped tremendously in the elections. Sadly, the Democrats could not bring themselves to set the terms of debate, and playing on the Republicans' terms meant a deserved defeat.
Update: Lexington of The Economist interviewed voters in Kentucky. Here's one:
Clinton Gray, a retired army Apache helicopter pilot, talked of being a “firm capitalist”, casting a vote in opposition to government-loving Democrats who “do not believe in industry,” and “do not want to see the economy improve, because it won’t be to their political advantage.”Well, Obama wanted the economy to improve - the Republicans did not, because it wasn't to their political advantage. If the Democrats had been competent in messaging, Mr. Gray might have understood he had it exactly backwards.