Off year elections are as important as years with Presidential elections. What can Obama do to get his coalition to vote in a mid-term election?It's a great question, so I wanted to highlight it, but I'm not sure I have much of an answer. So instead I'll give four answers.
One answer is: not much. It's just a basic truth that different demographic groups vote at different rates, and that midterms are lower-interest elections than presidential contests. So you're going to get fewer voters, which in practice means that you'll still get the every-time voters but far fewer of the sometimes voters.
The next answer is: electioneering probably can't do very much, but it almost certainly can make small differences on the margins. Which could be important! So, sure, run the best campaign that they can; the president can probably help the most by involving himself (carefully) in candidate recruitment and, yes, fundraising.
The third answer is: it may be less important than you think. Yes, it's true that midterm electorates are likely to lean more Republican, but we only have to go back to 2006 to find a Democratic landslide in a midterm. The biggest problem for Democrats in 2014 isn't that midterms are bad for Democrats; it's that midterms are bad for the party in the White House.
And the fourth answer is: the biggest thing that Obama can do to help Democrats in the midterms is to be a very popular president. Worked for Bill Clinton in 1998, and George W. Bush in 2002; failure to be a popular president had a lot to do with midterm disasters for Bush's party in 2006, Clinton's in 1994, and Ronald Reagan's in 1982. I suppose that's just obvious, but sometimes obvious is the truth.