It depends on how obvious the lie is. If someone says "The earth is both flat and made of cheese", they are so obviously wrong that you could afford to just rely on the reader's common sense. But if they say "the economy grew by Y percent for the first time in Z years", it's unlikely the reader has the facts necessary to recognize this as a lie immediately on hand.

For less obvious lies, it would be helpful to lead with the truth (see the primacy effect on memory). After stating the truth, then you can say "but politican X said Y".