Michael Barone: Dems have retreated to the coasts, and the GOP rules everything in between. Try his map exercise.

Get an outline map showing the 50 states and take a look at the latest poll averages in pollster.com in each race for senator and governor. Color in the percentage (rounded off; no need for tenths) by which either the Republican or Democratic candidate is leading (I use blue for Republicans, red for Democrats) in each state.
The results are revealing, even breathtaking.
The map of the Senate races shows Republicans leading over almost all the landmass of America. Democrats are ahead in the three West Coast states and Hawaii (though not by much in California and Washington) and by 1 point in Nevada. They're also ahead in four states along the Atlantic Coast -- Maryland, Delaware, New York, Connecticut -- plus Vermont.
Republicans lead in all the other Senate races, from Philadelphia to Phoenix and Boca Raton to Boise. True, their candidate leads by only 1 point in Barack Obama's home state of Illinois. And they've got narrow leads in some mountain states (West Virginia, Colorado, Kentucky).