US President Donald Trump kicked off the Republican Party’s midterm campaign season in Dallas on Wednesday night, headlining the opening of a highly unusual convention aimed at rallying voters ahead of November’s high-stakes battle for control of Congress. “This has been the most successful two years financially and every other way in the history of the presidency,” he said, as the crowd chanted “USA! USA!” In the almost two-hour-long speech, Trump also made a bold promise to give every adult...