US President Donald Trump faced a test of his political influence on Tuesday in a special congressional election in Ohio that became a referendum on his leadership and a last chance to gauge Democratic strength ahead of November's midterm elections. The Ohio race for a US House of Representatives seat headlines a day of voting across the country that also features primaries in four other states. Trump charged into the Ohio race, the final special election before November. A Monmouth poll last week showed the race was essentially a dead heat, down from a double-digit advantage for Balderson a month ago. Trump again pushed Balderson in an early morning tweet before voting began.