Here are some of the demographic differences between the 2008 presidential race and the 2010 congressional elections, as compiled by the National Election Pool, a consortium of news organizations that conducts interviews with voters as they exit the polls on Election Day. These results underscore the importance of turnout, which could be even more critical  to the outcome this year.

Pennsylvania:

                                                                       2010                           2008

White                                                             86%                          81%          (McCain won 51%-48%)

Black                                                                9%                          13%           (Obama won 95%-5%)

18-29                                                             13%                          18%          (Obama won 65%-35%)

65 and older                                              23%                           15%          (McCain won 50%-49%)

Democrats                                                 40%                           44%

Republicans                                               37%                          37%

Ohio:

18-29                                                            12%                           17%          (Obama won 61%-36%)

Democrats                                                 36%                           39%

Republicans                                              37%                           31%

Iowa:

18-29                                                           10%                             17%         (Obama won 61%-36%)

65 and older                                             24%                             18%

Democrats                                                 31%                              34%

Republicans                                              35%                              33%

White evangelicals                                 37%                              31%        (McCain won 65%-33%)

Colorado:

Latino                                                          12%                               13%        (Obama won 61%-38%)

65 and older                                             22%                               13%        (McCain won 53%-44%)

Florida:

White                                                           74%                                71%      (McCain won 56%-42%)

Black                                                            11%                                 13%      (Obama won 96%-4%)

Latino                                                         12%                                 14%      (Obama won 57%-42%)

18-29                                                            8%                                  15%      (Obama won 61%-37%)

65 and older                                            35%                                  22%      (McCain won 63%-46%)

Democrats                                                36%                                  37%

Republicans                                             36%                                  34%

Virginia:

18-29                                                          10%                                   21%      (Obama won 60%-39%)

65 and older                                            18%                                    11%       (McCain won 53%-46%)

Democrats                                                33%                                    39%

Republicans                                             37%                                    33%

White Evangelicals                                34%                                    28%      (McCain won 79%-20%)

(Albert R. Hunt is Washington editor at Bloomberg News and a Bloomberg View columnist. Follow him on Twitter.)

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