History suggests that beating Donald Trump in 2020 could be a tall order for Democrats - because voters tend to vote for presidential candidates with a height advantage over their opponent.

While it may sound superficial, taller presidential candidates have fared better over the years, with the taller of the two candidates winning the popular vote in two-thirds of elections, and in the electoral college more than half of the time.

That’s good news for Mr Trump, who stands at 6ft 3in, towering over Democratic frontrunners such as Joe Biden (6ft), Elizabeth Warren (5ft 8in), Bernie Sanders (6ft).

A quick glance at the height charts of recent political players bolsters the case; Mr Trump is taller than Hillary Clinton, Barack Obama was taller than John McCain, while Robert Kennedy was taller than Richard Nixon.

The longest serving president in US history was Franklin D Roosevelt, standing at a formidable 6ft 2in.

The Queen with US presidents: Truman to Trump Show all 23 1 /23 The Queen with US presidents: Truman to Trump The Queen with US presidents: Truman to Trump Eisenhower President Dwight D Eisenhower welcomes the Queen to Washington on 18 October 1957 AFP/Getty The Queen with US presidents: Truman to Trump Truman President Harry Truman welcomes then Princess Elizabeth to Washington on 4 November 1951 PA The Queen with US presidents: Truman to Trump Eisenhower President Dwight D Eisenhower and the Queen inspect a Guard of Honour at the gates of Balmoral Castle on 28 August 1959 Getty The Queen with US presidents: Truman to Trump Eisenhower President Dwight D Eisenhower with the Queen at Balmoral Castle on 29 August 1959 PA The Queen with US presidents: Truman to Trump Kennedy President John F Kennedy and wife Jacqueline with the Queen and Prince Philip at Buckingham Palace on June 5 1961 PA The Queen with US presidents: Truman to Trump Nixon The Queen and then Vice President Richard Nixon share a laugh at a Thanksgiving Dinner at Winfield House, the US ambassador's residence in London on 27 November 1958 PA The Queen with US presidents: Truman to Trump Nixon President Richard Nixon meets the Queen and Prime Minister Edward Heath at Chequers on 3 October 1970 Getty The Queen with US presidents: Truman to Trump Ford The Queen waves to the crowd as she and Prince Philip are welcomed to the White House by President Gerald Ford and wife Betty Ford on 7 July 1976 PA The Queen with US presidents: Truman to Trump Carter President Jimmy Carter and the Queen at a state dinner at Buckingham Palace on 7 May 1977 PA The Queen with US presidents: Truman to Trump Reagan President Ronald Reagan goes riding with the Queen at Windsor on 8 June 1982 PA The Queen with US presidents: Truman to Trump Reagan President Ronald Reagan riding with the Queen at Windsor on 8 June 1982 PA The Queen with US presidents: Truman to Trump Reagan President Ronald Reagan addresses a banquet at Windsor Castle on 8 June 1982 PA The Queen with US presidents: Truman to Trump Reagan President Ronald Reagan is pictured with the Queen and Prime Minister Margaret Thatcher before a banquet at Buckingham Palace on 9 June 1984 PA The Queen with US presidents: Truman to Trump Bush (H W) President George H W Bush waves to the crowd as he takes the Queen and Prince Philip to a baseball game in Baltimore on 15 May 1991 AFP/Getty The Queen with US presidents: Truman to Trump Bush (H W) The Queen shares a joke with former first lady Barbara Bush as she and former president George H W Bush attend an awards ceremony in London in November 1993 AFP/Getty The Queen with US presidents: Truman to Trump Clinton First Lady Hillary Clinton talks with the Queen at Buckingham Palace on 30 November 1995 AFP/Getty The Queen with US presidents: Truman to Trump Clinton President Bill Clinton and the Queen pose for a photo at the Guildhall in London before a banquet to commemorate the 50th anniversary of the D-Day invasion in 1995 AFP/Getty The Queen with US presidents: Truman to Trump Bush (W) The Queen waves to the crowd as she and Prince Phillip are welcomed to the White House by President George W Bush and wife Laura Bush on 7 May 2007 PA The Queen with US presidents: Truman to Trump Bush (W) President George W Bush and wife Laura Bush with the Queen and Prince Philip on a state visit on 19 November 2003 AFP/Getty The Queen with US presidents: Truman to Trump Obama President Barack Obama looks on as the Queen signs a guestbook after a dinner at Winfield House, the US ambassador's residence in London on 25 May 2011 AFP/Getty The Queen with US presidents: Truman to Trump Obama The Queen and President Barack Obama arrive at a state banquet at Buckingham Palace on 24 May 2011 AFP/Getty The Queen with US presidents: Truman to Trump Obama The Queen and Prince Philip welcome Barack and Michelle Obama at Buckingham Palace on 1 April 2009 AFP/Getty The Queen with US presidents: Truman to Trump President Donald Trump and the Queen inspect a Guard of Honour at Windsor Castle in July 2018 PA

The sputtering, aborted long-shot run by New York City mayor Bill de Blasio looks, in light of these facts, to have been a missed opportunity. Almost.

There are, of course, exceptions to the rule. Mr Obama is 6ft 1in, shorter than 2012 opponent Mitt Romney. Mr Obama still edged the popular vote and won a convincing electoral college haul.

Meanwhile the towering Al Gore won the popular vote in 2000, but George W Bush became president thanks to his electoral college tally.

The psychology behind all of this appears fairly obvious - taller people are typically seen as more physically formidable.

In a Leadership Quarterly research paper on the subject, the authors said: "The advantage of taller candidates is potentially explained by perceptions associated with height: taller presidents are rated by experts as 'greater', and having more leadership and communication skills. “We conclude that height is an important characteristic in choosing and evaluating political leaders."

The rival Mr Trump hit particularly hard during the Republican primary was Jeb Bush, who, at 6ft 3ins, may have appeared like a physical as well as a political threat during the face-to-face debates.

His distaste for shorter politicians was also clear during the process - he slapped a label of ‘Little Marco’ on Marco Rubio at every opportunity.

And, as diminutive former New York mayor Michael Bloomberg dipped his toe into the 2020 water last week, Mr Trump remarked: “Little Michael will fail.”

There is, however, one former president who Mr Trump is willing to concede was greater than himself; Abraham Lincoln.