On June 24, Kelly Loeffler, an incumbent Republican senator and WNBA team owner, criticised the Black Lives Matter movement for being a “very divisive organisation” promoting “violence and destruction across the country”. In doing so, she kicked off a summer-long standoff with the WNBA and its players. After a Yahoo article asked on June 29 “why Kelly Loeffler [was] still a WNBA co-owner”, considering her comments, players got involved. Star players asked Loeffler to step down and re-emphasised the league's commitment to dedicate its season to the “Say Her Name” campaign and to Breonna Taylor.

But on August 4, WNBA players shifted their strategy. Arguing that Loeffler was criticising the WNBA to win over conservative voters, players began actively supporting one of her opponents, the Reverend Raphael Warnock. In August, most of the league wore “Vote Warnock” T-shirts on national television and discussed their reasons for supporting him in many interviews from August to Election Day. Warnock’s polling and donation numbers started rising over the summer. In November, he forced Loeffler into a run-off election, to be held in January. Warnock recently said that the WNBA’s decision to support him was a “turning point” in his campaign.

Was that really because of the WNBA? Many things started going right for Warnock during the summer aside from the players’ support. My research suggests that Warnock is right: WNBA support made the difference.

• Looking at raw donation numbers won't tell us what made the difference

Warnock noted that, in the 48 hours after the WNBA's August. 4 T-shirt campaign, his campaign raised $183,000 and attracted 3,500 new grassroot donors. In fact, in both late June, when the WNBA criticised Loeffler, and early August, when the players began supporting Warnock, his campaign raised a great deal in donations, with high dollar totals and high numbers of donors.

But these high-donation periods may have been driven by other factors. Warnock's platform centred on healthcare and civil rights during a pandemic and a renewed reckoning with race in America. Democrats in general were having good news cycles, good polling numbers had come out, the election was getting closer, and donor groups were more active. Loeffler was already in the news for her anti-BLM statements before the WNBA picked up the fight. On July 30, Warnock got national attention when he delivered the eulogy at John Lewis's funeral. All these events likely also drove donations to Warnock.

• Here’s how I did my research

To isolate the WNBA’s effect on donations, I used various statistical methods and Federal Election Commission data to measure the jump in donations at two key points compared with two benchmarks: how much the Warnock campaign was already raising, and how much other Democratic candidates in toss-up Senate races raised during the same period.

I found that after the June 29 Yahoo article kicked off WNBA mobilisation, the Warnock campaign saw a 10 per cent increase in daily donations over its previous daily averages, for an additional $25,000 in the 48 hours following the league and players’ criticism of Loeffler. Similarly, after the WNBA’s T-shirt campaign, Warnock’s campaign brought in 20 per cent more than what the campaign had been getting in previous days, for a boost of $40,000 in the 48-hour window.

These are conservative estimates. WNBA-inspired donations could have kept pouring in for the next days or weeks. But isolating those as direct effects becomes impossible at that point.

Overall, the WNBA's effect was small. Other campaign events boosted donations much more. For instance, after Barack Obama endorsed Warnock on September 25 and new polls showed him leading the race for the first time, his campaign received a $250,000 surge over 48 hours, for a 40 per cent increase at the time.

But the WBNA's support boosted the campaign at a crucial moment.

• WNBA players changed the financial dynamics of the campaign

While Loeffler mostly funded her own campaign, some of her best fundraising days came after her anti-BLM comments and the WNBA’s response to them. That nationalised the race. The Warnock campaign’s 10 per cent donation boost after June 29 came almost entirely from political action committees and national activist groups. But in August, when the WNBA switched from criticising Loeffler to supporting Warnock, his campaign saw an increase in grassroot donations. A little more than 50 per cent of the extra boost to Warnock’s campaign on August 4 can be attributed to individual donations, mainly from within Georgia.

• Did these gains translate to the polls?

According to polling data from FiveThirtyEight, August is when Warnock’s support began climbing, separating from his Democratic opponent in the race, Matt Lieberman, and eventually overtaking the two Republican front-runners, Loeffler and representative Douglas A. Collins. It is impossible to isolate the effect of the WNBA’s support from the Warnock campaign’s other positive developments over the summer. We can assume, however, that the WNBA contributed.

In 2020, all sports leagues dove into a summer of activism. The NBA wore social-justice messages on their jerseys, boycotted play-off games after Kenosha, Wisconsin police shot and killed Jacob Blake, and offered their arenas as November voting places. More players in the National Hockey League, National Football League and Major League Baseball chose to kneel during the national anthem in protest of police brutality towards blacks.

Recent research finds that professional athletes' statements on criminal justice reform, police brutality or the BLM movement can change people’s attitudes on these topics. And the WNBA appears to have contributed to boosting its candidate into a run-off election against Loeffler.

• Angele Delevoye is a PhD candidate in political science and quantitative methods at Yale University. For other analysis and commentary from The Monkey Cage, an independent blog anchored by political scientists from universities around the country, see www.washingtonpost.com/blogs/monkey-cage