WASHINGTON (Reuters) - Even before U.S. Rep. Mark Foley (news, bio, voting record)'s cybersex scandal, Republicans fighting to keep control of Congress were struggling to hold on to "values voters" who usually are energized by issues like gay marriage and abortion. While such issues motivated the Republicans' social-conservative base in the past, they are overshadowed in this year's congressional election campaign by concerns about the Iraq war, the economy and national security, according to opinion polls and political strategists. "Poverty, the wealth gap, health care -- people can't afford Medicare. Something's got to be done about that," Sue Harrell, a...