Ted Cruz has a powerful tool as he tries to close the deal with Iowa voters: He has aired the most effective TV ads in the Republican presidential race, according to independent research by a private company. The ratings come from Ace Metrix, a television analytics company that uses large online panels to rate the effectiveness of TV commercials. The company's political unit found that Cruz's campaign produced five of the 11 top-scoring ads among Republican voters this election, including the single most effective ad of the GOP primary so far...
