WASHINGTON (AP) — President Barack Obama is lending his voice to national radio ads by the Democratic National Committee, seeking to motivate African-American, female and other voters who tend to sit out midterm elections. Future spots were set to target Hispanics, Asian Americans, younger and female voters — all constituencies that tend to be reliably Democratic voters, but who typically are infrequent voters in non-presidential campaigns. From equal pay to affordable health care to immigration, the stakes in this election could not be higher — and we look forward to communicating that contrast over the coming weeks. The DNC's messages are designed to motivate groups that helped Obama win two terms as president but whose enthusiasm wanes in off-year elections. [...] that advertising was expected to come from candidates, party campaign committees and well-funded outside groups such as Americans for Prosperity and Ending Spending Action Fund.