The Guardian view on Kamala Harris’s vice-presidential pick: Tim Walz is a smart choice for Democrats | Editorial

Kamala Harris's own ascension to the top of the ticket has shone a brighter spotlight than usual on the Democrats' choice of vice-presidential nominee, underlining why the second slot on the ticket matters. The impact of the running mate is usually limited unless they prove extraordinarily popular or unpopular. Growing concerns about the state of the US economy are likely to be far more consequential. But Ms Harris's selection of Minnesota's governor, Tim Walz, on Tuesday, and the enthusiasm it is engendering, contribute to the sense of a rejuvenated campaign. Democrats are not taking poll improvements for granted, but now believe that it is possible to beat Donald Trump.

Ms Harris stressed Mr Walz's record of "fighting for middle-class families". Originally from rural Nebraska, he is a former teacher and high school football coach who served in the army national guard for 24 years. As governor he has overseen - with Minnesota's Democratic legislature - progressive policies including free school meals, abortion protections, pro-worker policies and gun restrictions. He has a better record on facing the climate crisis than rivals.

He has been adept at winning over moderate Republicans, but also at attacking Donald Trump; Ms Harris's description of the former president as "weird" was borrowed from him. The right has already argued that he should have been swifter to call in the national guard when protests following George Floyd's murder by a police officer in Minneapolis turned violent. But the Trump campaign will surely find that the tag of "dangerously liberal extremist" is harder to pin on a folksy white Midwestern man who loves hunting than on a black woman from California. Critically, Mr Walz also has significant political experience and ties, having first been elected to Congress in 2006; friends there rallied behind him.

Vice-presidential nominees tend to be important primarily in how they reflect on their boss and balance the ticket. JD Vance was meant to bring a shot of youthful energy when Mr Trump was running against Mr Biden; with Ms Harris as the de facto Democratic nominee, it is his extreme stance on abortion and remarks on "childless cat ladies" that grab attention. The disastrous bet on Sarah Palin threw doubt on John McCain's judgment, experience and leadership. People need to believe that, in a crisis, the running mate would be capable of running the show: around one in five US vice-presidents have taken over under such circumstances.

While some suggested that other candidates - notably Josh Shapiro, the Pennsylvania governor and reportedly the other finalist for the role - would bring a swing state with them, political scientists suggest that is a myth. Christopher Devine and Kyle Kopko, who analysed election data going back to the late 19th century, suggested that "the vice presidential home state advantage is, essentially, zero".

What vice-presidential picks can do is enthuse the party and help to establish a sense of unity and direction. Mr Walz was the most progressive of the Democratic politicians seriously considered for the role. While activists lobbied against other candidates, there appears to be real enthusiasm about both what he stands for and his ability to communicate that straightforwardly. Ms Harris's pick contributes to a renewed sense of purpose, and is another welcome step in a campaign that still has a long way to run.