Quick answer: pretty much everything.
When I was phonebanking in 2010 for OFA (Obama For America) in Wisconsin, the unified campaign effort was tasked with electing a Democratic governor, re-electing Senator Russ Feingold (D-WI), and electing Democrats to the House of Representatives. The phone script included this: “Please vote to send people to Washington DC who will help President Obama advance his agenda”.
On the list of people we were calling were those who had voted for President Obama in 2008, people who should have been interested in advancing his agenda because, in theory, they voted to do just that only two years before.
But mid-terms are funny things. Many of the people I called said they only voted in presidential elections. Some of them were unhappy because
they didn’t get their pony so much of the president’s agenda had to be set aside to deal with the worst financial crisis since the Great Depression … a parting “gift” from Worst President in History George W. Bush.
Well, Democrats were not enthused but Republicans were because they had two things firing up their base: a black man (who was not even born in ‘Murica!!) had stolen the election (ACORNNNN!!) … and the Affordable Care Act had been passed, ushering in death panels and government-run health care and frightening all your doctors into fleeing to the libertarian paradise of Somalia.
So turnout was low and we ended up with Scott Walker and a solid Republican legislature here in Wisconsin. And we sent Ron Johnson to the Senate and Sean Duffy and Reid Ribble to the House of Representatives. Elsewhere, Michigan got Rick Snyder, Ohio got John Kasich, Pennsylvania got Tom Corbett, Florida got Rick Scott, Iowa got Terry Branstad, Maine got Paul LePage … and America got Republican Speaker of the House John Boehner.