US election 2016: why this election will make history

 It took a while, but now we finally know which two candidates will fight it out in the race for the White House.Short of a shock at the Republican convention in July, Donald Trump will be the Republican candidate, something few would have predicted 12 months ago.And this week, what had seemed likely for some time was confirmed: Hillary Clinton is the Democratic candidate.Whatever happens from this point on, the outcome will be historic. This is how. 

 When Barack Obama first walked through the White House front door back in January 2009, he was aged 47, and was the fifth-youngest president in history. Theodore Roosevelt was the youngest, at 42 years and 322 days.The next one will be a fair bit older, whatever happens.Donald Trump celebrates his 70th birthday on 14 June. If elected in November, he would be the oldest president in history (Ronald Reagan was 69 when he took office).Hillary Clinton, meanwhile, turns 69 some two weeks before the election, and would become the second-oldest president on inauguration. She would replace William Henry Harrison, who became president in 1841 (and was the last president born on British soil). 

 Trump v Clinton is the first presidential contest between New Yorkers since 1944, when the governor of New York, Thomas E Dewey, ran against the incumbent, Franklin D Roosevelt.Whoever wins this time will become the first New Yorker in office in 71 years when the inauguration takes place next year.(And yes, we know Mrs Clinton was born in Chicago, but she was a senator from New York and lives in the state.) 

 If Mr Trump wins, we could be looking at the least amount of money spent by a winning candidate for some time.Federal Election Commission records show he spent $49m (£34m) up to the end of April, of which $36m is his own money.No other candidate since Al Gore in 2000 ($126m) has spent as little. Hillary Clinton is on some $187m so far, by the way.Of course, Mr Trump could break out the chequebook given that he has more campaigning to do between now and November, but it looks likely he will come a long way under what Barack Obama spent last time round - almost $556m. 

Democrat relay?

Amazingly, only two Democrats have directly succeeded another Democrat as US president. The most recent was James Buchanan, who was president from 1857 to 1861.Harry Truman and Lyndon Johnson were both vice-presidents who were named president when their predecessors died. They both then went on to win the next election.A Clinton win, therefore, would bring even more significance to the Democratic Party.

So who is likely to win?

This is how polls have changed over the past 10 months between the two frontrunners. Now there's only five months to go.