Why Harris picked Walz as her VP and what that means for her candidacy

It was not long ago that Kamala Harris was still running for re-election as vice president of the United States, alongside President Joe Biden. Following Biden's withdrawal from the race, Harris has now become the Democratic Party's nominee for president.

And today, she chose her own vice president: Minnesota Governor Tim Walz.

Walz's selection concludes an intensive, two-week "vetting" process in which Harris and her vice-presidential search team researched and met with more than a half-dozen finalists to determine who would be the best running mate for the presidential campaign, and governing partner in the White House.

The shortlist itself provides some hints as to what Harris was looking for.

All six finalists, unlike Harris, were white men, and four were state governors (Josh Shapiro of Pennsylvania, Andy Beshear of Kentucky, J.B. Pritzer of Illinois, and Walz).

Three came from competitive, or "battleground," states, including Shapiro, Walz, and Arizona Senator Mark Kelly. Clearly, Harris wanted a running mate who could balance the ticket demographically, help to win the election, and help her govern once in office.

Many people thought Shapiro—who checks all of those boxes—was the obvious choice for vice president. He was elected governor in 2022, while serving as attorney general, and has represented Pennsylvanians in state and local office for more than 20 years.

Shapiro's most appealing credential is his popularity among voters in Pennsylvania—a critical swing state that could decide whether Harris or her Republican opponent, former President Donald Trump, wins the November election.

With a 60 percent approval rating, Shapiro seemed likely to deliver Harris a victory in that state, and with that the presidency, perhaps.

Why Walz?

Harris chose Walz instead. What does this tell us about her as a candidate and potential president?

First, Harris picked the best-qualified candidate for the vice presidency. Walz is a second-term governor who previously served for 12 years in the United States House of Representatives. He is also a 24-year military veteran and was once the ranking member on the House Veterans' Affairs Committee.

Walz was the only vice-presidential candidate who had served in federal and state government. He brings executive experience to the White House as a governor, and foreign policy experience as a former member of Congress.

In the latter role, Walz opposed the invasion of Iraq and US military actions in Syria. He is generally supportive of Israel and, following the October 7 Hamas-led attack, affirmed Tel Aviv's "right to defend itself". However, Walz has also expressed openness to criticism of Israel’s military offensive in Gaza and support for a potential ceasefire.

Shapiro, by comparison, is a first-term governor who has never served in federal office. While voters likely would have found him and other vice-presidential finalists to be well-qualified, Walz is best prepared to serve as "second in command" in Harris's White House, and even take over as Commander-in-Chief if necessary.

Some Democratic voters also may have objected to Shapiro’s criticism of campus protesters against the war in Gaza, although he has also been critical of Israeli Prime Minister Benjamin Netanyahu.

Running mate benefits

My book with Kyle C. Kopko, Do Running Mates Matter? shows that Harris is likely to benefit in this election from Walz's credibility as a potential vice president.

Voters expect a running mate to be well-qualified for the job, above all else. When presidential candidates deviate from this standard, perhaps in a desperate gamble for short-term electoral advantage, voters think less of them and are less willing to vote for them.

This is precisely what happened to the Republican presidential candidate in 2008, John McCain, when he chose Sarah Palin, the first-term Governor of Alaska, as his running mate.

That same year, his relatively inexperienced Democratic opponent, Barack Obama, chose an eminently qualified running mate in Biden. Voters thought better of Obama's judgement as a result, and became more willing to vote for him. Harris's choice of Walz may have the same effect.

Second, Harris chose someone who shares her progressive political values. Walz has governed as a progressive in Minnesota, and won the vice-presidential endorsements of Nancy Pelosi and Bernie Sanders.

It is likely that he will see eye to eye with Harris, who was once rated the most liberal member of the US Senate and in 2020 was viewed by voters as well to the left of Biden.

Too liberal?

This will be reassuring to the base of the Democratic Party. However, it may be concerning to the moderate and undecided voters who could decide this year's election.

Picking a relative moderate for vice president, such as Shapiro or Kelly, might have reassured those voters and—as our research shows—shifted perceptions of Harris's ideology toward the centre. But at what cost?

Doing so could have alienated the party base and cost Harris some of her most reliable supporters. Building and maintaining a winning electoral coalition requires difficult decisions, and the best strategy is not always clear.

By picking Walz, Harris seems to be doubling down on her progressive brand. This may help communicate a more consistent message to voters about what to expect from a Harris Administration, and minimise friction once in office.

'Attack dog'

Third, Harris chose someone who can take the fight to Republicans in this campaign, and beyond.

Vice-presidential candidates are often known as "attack dogs"—going after the other party while the presidential candidate remains dignified and above the fray. Harris, the former prosecutor, knows she cannot quite do that while running against Trump.

But she does need to have by her side an effective communicator who is capable of parrying Republican attacks while still appealing to voters and staying on message.

Walz, the quintessential "happy warrior," has demonstrated a remarkable ability to do just that while auditioning for the VP slot in recent weeks—most notably, when he introduced a new and surprisingly effective line of attack against Trump and Vance by describing them as just plain "weird."

If elected, Harris and Walz will still need to communicate well with the American public and respond to Republican attacks, while pursuing their legislative agenda.

Walz's performance thus far suggests that he could be an asset as vice president, in style as well as substance.

It is too soon to tell whether Harris's choice of Walz for vice president was the right one. Only later can we judge whether he helped her to win the election and, if so, to govern in the White House.

For now, the selection is important because it tells voters a great deal about what kind of president Harris would be, and whether she deserves their vote.

She has chosen, in Walz, a credible vice president who shares her progressive values and would not shy away from criticising the Republican alternative. In doing so, she has given Americans a clearer vision of what the next three months of this campaign will look like—and perhaps the next four years.