As states reopen after coronavirus-related shut downs, the presidential election campaign is starting up again as well. The Trump campaign has announced rallies — starting in Tulsa, on Saturday.

In 2016, these rallies were the cornerstone of Trump’s campaign. As president, Trump has continued to hold this type of rally on a regular basis. While going back on the stump is a major part of Trump’s 2020 campaign strategy as well, do rallies actually help Trump?

In a forthcoming article in the Journal of Politics (co-written with Brenton D. Peterson), we argue Trump’s campaign visits actually have mixed effects. We measure the effect of candidate visits in the 2016 election to determine their impact.

Here’s what we found: While Trump visits do indeed mobilize his supporters, they also counter-mobilize support for his opponent. Crucially, this counter-effect is bigger.

How do you measure the effect of campaign visits?

Political scientists have long tried to gauge whether public campaign appearances by candidates boost electoral outcomes. The findings have been mixed: Some studies have found positive effects. Others find mixed effects, or evidence there are zero benefits to campaign visits.

For example, in a previous article written by two of us, we find visits by Harry Truman in the 1948 campaign resulted in a 3 percentage point increase in votes at the county level. However, visits by his opponent Thomas Dewey had no effect.

Typically, researchers see this as an either/or scenario: A campaign visit either helps a candidate or does nothing to boost their standing on Election Day. But there’s another factor to consider. A visit could also activate supporters of the candidate — as well as those of their opponents.

That’s a problem when we try to measure the effect of campaign visits on election results, because election results inherently only allow us to measure the net effect of a visit on local results — meaning, any increase of support minus any increase in opposition.

In the article, we try to solve this problem by instead looking at campaign donations — which campaigns report directly to the Federal Election Commission. If voters on both sides feel strongly about a particular candidate making a visit, we should see an increase in donations not just to that candidate, but also to their opponent on the day of that visit.

Trump campaign visits in 2016 also mobilized donations by Democrats

We find this is exactly what happened with Trump’s 2016 visits. During the campaign, both Hillary Clinton and Donald Trump made many stops across key swing states like Florida, Michigan and Pennsylvania — though Trump was considerably more active (158 visits) than Clinton (88 visits).

On the day of these visits, donations to both Trump and Clinton increased in the media markets they visited.

Specifically, Clinton’s visits increased donations by an average of 16.2 percent — or approximately $9,613 per visit to her own campaign on the day of the campaign visit. Meanwhile, Trump rallies resulted in just a 5.5 percent increase in day-of-visit donations to his campaign.

However, there was also a notable anti-Trump effect when Trump visited. On average, on the days and in the areas that Trump visited, donations to the Clinton campaign also went up by about 7 percent, or $3,388 per Trump visit.

Given Trump’s rally-heavy campaign schedule in 2016, this suggests the Republican candidate helped raise about $500,000 for the Democratic presidential campaign. Additionally, Trump’s visits appeared to raise considerably more money for Clinton’s campaign than they raised for his own.

Trump’s rallies have mixed effects

To be sure, there are a number of caveats to these findings. First, these are very small amounts for presidential election campaigns, and unlikely to have made a major difference to the campaign.

Second, Trump’s rallies have clear value beyond local mobilization. His rallies are often televised live, providing him with free national media coverage.

Third, we make no claims in this study about how these visits affected vote choice. It’s possible the people who donated were always going to vote anyway — in which case, Trump’s visits may have had no real effect on Election Day. However, it is possible that some of the people who were mobilized by these visits to donate to Trump or to Clinton also became more active participants in other ways, perhaps by volunteering or donating more later in the campaign cycle.

But our findings do suggest Trump’s campaign trail activities have mixed effects. While his rallies might energize some of his supporters, they also activate his opponents. Notably, another recent study found very similar effects for Trump’s endorsements in the 2018 election cycle.

Why do Trump rallies energize the opposition?

We think negative partisanship might be energizing Democrats. This means a voter’s dislike of Trump, in particular, activates them to support their own candidates. Trump, as a strongly polarizing political figure, might be a bigger source of such negative feelings than previous presidential candidates. Therefore, his personal appearances might also activate Democrats more.

What does this mean for rallies like the one Trump is planning to hold in Oklahoma? When Trump heads back out on the stump, he is probably activating political activity among his own local supporters. But he’s also likely to activate Democratic voters who oppose him — and possibly to such an extent that the counter-mobilization outweighs the mobilization effect. If so, at the very least, Trump might be helping Biden raise some money.

Boris Heersink is an assistant professor in the Department of Political Science at Fordham University. Follow him on Twitter @Boris_Heersink.

Jordan Carr Peterson is an assistant professor in the Department of Political Science at North Carolina State University. Follow him on Twitter @JordanCarrP.