PARIS (Reuters) - Right-wing leader Nicolas Sarkozy goes into France's presidential election on Sunday with a narrow lead over Socialist Segolene Royal in most opinion polls, but with millions of voters still unsure whom to back. Most polls before a campaign blackout on Friday night showed Sarkozy, 52, a few percentage points ahead of Royal, 53, and indicated they would contest a run-off on May 6. One poll predicted a dead heat between them. Surprises cannot be ruled out because the surveys suggested up to a third of the 44.5 million voters were not sure of their choice, giving hope...