WASHINGTON (Reuters) - The Senate's repudiation of a gun industry legal protection bill this week gave the National Rifle Association an unexpected blow and injected gun policy into this year's elections. Lawmakers, lobbyists and experts on gun politics said the odd spectacle of pro-gun senators stampeding to kill their own legislation will have repercussions at the ballot box. Both Massachusetts Sen. John Kerry, the presumptive 2004 Democratic presidential nominee, and Sen. John Edwards of North Carolina, then still in the White House race, interrupted their campaigns to cast gun control votes on Tuesday. Kerry gave a blistering speech accusing President...