CONWAY, Arkansas -- In what is likely to become a theme of the last weeks of campaigning before the midterm elections, former President Bill Clinton all but begged voters here in Arkansas not to use their vote as an expression of disapproval for Barack Obama.The president is playing an outsized role in the race between Arkansas Democratic Sen. Mark Pryor and Republican challenger Rep. Tom Cotton. Obama is seriously unpopular here; a recent survey by the Democratic polling firm Public Policy Polling put his job approval rating at 31 percent, versus 62 percent disapproval.Given that, Cotton has relentlessly tied Pryor to Obama, saying Pryor has voted with the president "93 percent of the time" and is a reliable rubber stamp for anything Obama wants to do. The strategy has given Cotton a small but durable lead in the race; he has been ahead in eight of the last 10 public surveys.Democrats are feeling the heat, and the campaign against Obama was clearly on Clinton's mind when he addressed a crowd of at least 1,000 at the University of Central Arkansas.Clinton argued a vote for Cotton, whom he never mentioned by name, would be a vote against raising the minimum wage, against affordable interest rates for student loans, and against equal pay for women.