Republican Donald Trump and Democrat Hillary Clinton took big steps toward securing their parties' presidential nominations on Tuesday with a series of state-by-state victories, but their rivals vowed to keep on fighting.<br />Now they are under pressure to show they can unify voters in their respective parties and avoid a potentially disastrous split in their ranks that could hurt them in the Nov. 8 election.<br />US networks projected Trump won seven states with victories stretching into the deep South and as far north as Massachusetts, adding to a sense of momentum he had built last month by winning three of the first four contests.<br />Clinton's victories in seven states were just as impressive but in many ways predictable, propelled by African-American voters in southern states like Arkansas, where she and former President Bill Clinton began their political careers.
