The impact of the Obama campaign on white racial attitudes -- Part I. Documenting change in white racial attitudes during the 2008 campaign -- Is the decline in white racial prejudice meaningful? -- Visions of unity: white perceptions of race relations -- Part II. Explaining change in white racial attitudes during the 2008 campaign -- The role of mass media in changing white racial attitudes -- Testing rival theories of media influence -- Part III. Epilogue: White racial attitudes after the 2008 campaign -- Whatever happened to the Obama exemplar? -- Implications for the study of racial attitudes