Overnight, political betting markets have recorded a sharp increase in the implied probability of Minnesota Governor Tim Walz being selected as Vice President and presumptive Democratic presidential nominee Kamala Harris' running mate. According to electionbettingodds.com, which compiles data from Betfair, Smarkets, Polymarket, and PredictIt, Walz has a 41.5% implied probability of being named the Democratic VP candidate, behind only Pennsylvania Gov. Josh Shapiro at 54.1%.

• The spike in betting market activity on 5 August may have been due to a video circulated on social media showing several black SUVs at Walz's Minnesota residence. A similar increase in security was seen around Republican VP candidate JD Vance before his selection as former President Donald Trump's running mate.
• However, Tyler Pager at WaPo posted on X that he had received confirmation that the vehicles were part of Walz's home state security detail and not a sign that Harris had already picked him.
• As we noted on 5 August (see 'US: Shapiro Firms As Harris Veep Favourite', 1749BST), "Although conventional wisdom suggests that a vice-presidential selection is rarely consequential to a presidential election outcome, Shapiro's name on the ticket could materially benefit Harris in Pennsylvania, a state which is most likely to be the “tipping-point state” that determines the result."

Chart 1. Political Betting Market Implied Probability of Democratic Party VP Candidate, %

Source: electionbettingodds.com