If Republicans hope to cut into Democrats’ margins in the House in 2010, a good place to start will be the 49 districts that voted for both a Democratic House candidate and John McCain. As you might expect, many of these districts are in the South, Appalachia, rural Midwest and Mountain West. Many are represented by conservative Democrats who know and fit the district well, but the GOP certainly has a shot at knocking off some of the freshmen who rode in on Obama’s coattails.

Democrats, for their part, will surely target the 34 districts that voted for both President Obama and a GOP candidate. Most of these districts are in the upper Midwest and Northeast, although Republicans are becoming such an endangered species in the Northeast that Dems may have a tough time finding additional targets.

Here are two maps produced by CQ Politics, showing the presidential results by district and the House results. I’d like to develop a map at some point highlighting the districts that split votes, but for now you can compare yourselves: