US Election: Vice Presidents prepare to take the spotlight ahead of huge week

• Read all about what the VPs actually do

• VPs have a decent winning record when they run for President

• Why did the candidates pick Walz and Vance? Find out here!

• Get the latest data including current prices and volume of bets in our daily update

• View Betfair Exchange politics markets as you have never seen them before

What does a VP do, exactly?

A vice-president may not have much personal power - much of that depends on the President - but in a campaign, they can make an impact and signal to voters that their concerns are being met, and that they are not being ignored.

Constitutionally, the vice-president's role is limited

They are slated to assume the Presidency in case of death, resignation, or the incapacity of the President. For instance, many recent vice-presidents have been de facto President while the President is undergoing surgery or under general anesthesia.

In 2021, Kamala Harris was granted Presidential authority for an hour-and-a-half as Joe Biden undertook a colonoscopy.

The vice-president also takes a role as President of the US Senate, and has a tie-breaking vote in the chamber. This has proved particularly useful in the Biden administration, as the Senate was divided 50-50 between Democrats and Republicans. Harris broke multiple records for the most tie-breaking votes cast by an US VP.

In the midst of an election, however, a VP pick can bring much more to the table.

Practical considerations

A Presidential candidate will seek to have their VP pick complement their own voter base.

Barack Obama chose Joe Biden as his running mate in contrast to his own qualities. While Obama was only a few years into his national political career, Biden had served in the Senate for 35 years. Choosing a white politician veteran made sense to the Obama campaign.

A running mate might improve a candidate's chances of winning certain states.

Many people saw Hillary Clinton's choice of Tim Kaine as running mate in 2016 as courting voters in Virginia, Kaine's home state. Others also saw a benefit in his fluency in Spanish, as a way to appeal to Hispanic voters.

Trump has also played this balancing act, making judgements about where a running mate might complement his own qualities - but also bring critical votes with them.

In the 2016 election, Trump chose Indiana Governor Mike Pence as his running mate. As an Evangelical Christian, a long-standing politician in the House of Representatives and as Governor, and a resolutely conservative politician, Trump could count on him to counter the criticisms of his own candidacy.

Why did Trump pick Vance?

This time, Trump has wagered that the key Midwest battleground states would be best won by one of their own. When announcing JD Vance as his running mate, Trump recognised this - calling out Vance as a candidate who would fight for American workers "in Pennsylvania, Michigan, Wisconsin, Ohio, Minnesota, and beyond".

Other considerations made Vance an ideal candidate for Trump, too.

At 39-years-old, he is ideally-placed to counteract any worries that Trump himself is too old to run for President. His military service coupled with his Ivy League education gives him formidable credentials to govern - both of which Trump cannot claim.

Walz pick seemed obvious but Betfair markets did not predict it

For Harris' part, her choice of Tim Walz was the culmination of a contest where she considered a number of well-credentialed white males to complement her on the Democratic ticket.

Walz was Governor of Minnesota, a state in the Midwest of the United States - the same region as JD Vance's native Ohio. According to Axios, over the last two decades, the region has emerged as a key battleground in the Presidential election, and "the most purple region overall" - meaning that many of its states could swing towards either candidate on election day.

Yet in the 24 hours before being announced as the running mate, Tim Walz's odds were only at 3/14.00, implying only a 25% chance of being chosen.

Josh Shapiro, the Governor of Pennsylvania - a key swing state - was then at odds of 4/111.36, giving him a 73% chance of being chosen.

But the odds shifted rapidly on the day of the election. Others who were considered also came from key states in the Midwest - such as Pete Buttigieg from Indiana, or Andy Beshear from Kentucky (which is often considered a part of the Midwest). The other close candidate, Mark Kelly, is a Senator from Arizona, one of the seven swing states in this election.

History of VPs by election

Harris will take heart from her boss' example - he is one of six incumbent or former vice presidents to win the Presidency, giving her a decent shot.

In the last few decades, vice-presidents have become strong candidates for President.

Richard Nixon won the Presidency as a former vice president in 1960. Joe Biden did the same in 2020.

In total, 15 vice presidents have become President.

At 20/211.95, Kamala Harris is (just) the favourite to win this election for now - though the betting markets have shown how volatile the odds can be. Trump was the betting favourite for weeks before the debate, but during the 90 minute spectacle Harris overtook him where she remains today.

How will the VP Debate affect the odds?

Next week, the two candidates for Vice-President will face off in their only scheduled television debate, on October 1st in New York City on CBS News.

The two have never met in person, but they have had plenty to say about each other on the campaign trail.

The debate may be critical in boosting either campaign. The Harris-Trump debate saw the Presidential winner betting market change rapidly. Harris recaptured the lead 50 minutes into the debate - she started the night at 11/102.11 odds (48% chance) but ended outpacing Trump and reaching evens (50% chance).

Vance will be hoping to portray Walz as a radical leftist, criticising his response to Black Lives Matters protests in Minneapolis and some of the policies he enacted as Governor. On Walz's part, he is almost certain to use JD Vance's baseless claims of Haitian immigrants eating household pets as proof that Trump's running mate is as extreme as Trump himself.

Many political analysts are expecting this VP debate to be more consequential than previous such events, given how tight this election is and the impact that the Presidential debate earlier this month had on the betting odds and the polls.

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