PHILADEPHIA — President Donald Trump and Democratic challenger Joe Biden have one last chance to make their case to voters in critical battleground states on Monday, the final full day of a campaign that has laid bare their dramatically different visions for tackling the nation’s pressing problems and for the office of the presidency itself.The candidates are seeking to lead a nation at a crossroads, gripped by a historic pandemic that is raging anew in nearly every corner of the country and a reckoning over race. More …