Dads may be more likely to vote for female political candidates if they have a daughter—but only if the daughter is their first-born child.

That’s the finding of a new research paper in the journal Political Behavior.

In a second paper, which appears in Public Opinion Quarterly, the research team found that dads with daughters were more likely to support policies designed to increase gender equality—but again, only if the daughter was the first-born offspring.

Taken together, the impact of a child’s gender on her father’s politics is what the researchers call the “first-daughter effect.” The effect is stronger in Democrats than Republicans.

One especially surprising finding: the first-daughter effect made dads more likely to support gun control.

Both studies control for the influence of partisan preference and a range of other factors.

A new lens

“When men have a female child, it may give them a new lens through which to look at the world, where they may think, ‘Okay, what’s it like out there for a little girl?'” says coauthor Jill Greenlee, associate professor of politics and women’s, gender, and sexuality studies at Brandeis University.

“And from our data, it appears that there’s something about entering fatherhood with a female child that makes men think about gender in a different way. Perhaps they recognize gender discrimination for the first time, or perhaps they begin to think about it in a different way. It may be that they develop new insights into the ways that gender shapes opportunities differently for girls,” Greenlee says.

But why only first-born daughters?

“We need further research on this, but we have some hypotheses. We know from studies by other researchers that men spend more time with their first-born daughter than subsequent daughters,” Greenlee says.

“We also know that in general, men have less scripted relationships with their daughters than sons, which may mean they feel freer to spend their time differently with daughters than sons. So it may be that first-born daughters are uniquely situated to influence their fathers by virtue of the time that they spend together,” she explains.

“Research in political science shows that first experiences in politics tend to have a bigger impact on individuals. The first time people vote, for example, leaves a big imprint. Your first experience of becoming a parent may also have a lasting impact.”

Greenlee and her colleagues looked at the support among fathers for Hillary Clinton’s 2016 presidential campaign. Clinton directly appealed to dads, saying in a debate during the Democratic primary, for example, “Finally, fathers will be able to say to their daughters, ‘You, too, can grow up to be president.'”

Using survey data that the Cooperative Congressional Election Study (CCES) collected from 1,500 voters in 2016, Greenlee’s research team found that fathers with first-born daughters showed “significantly and substantively” increased support for Clinton.

The researchers also ran a survey experiment with a fictional candidate named Molly Smith running to become the first woman to represent Minnesota’s 10th congressional district.

Her appeal to voters echoed Clinton’s by emphasizing expanding opportunities for “our daughters.” Fathers of first-born daughters exposed to the “Clintonesque” appeal were significantly more likely to support Molly Smith than fathers of first-born sons.

The paper concludes that “Clinton’s appeals to fathers of daughters were indeed effective in the 2016 election. Ultimately, our results suggest that having a first daughter may be a transformative experience that leads men to… apply this newfound perspective to their candidate evaluations and vote choices.”

Dads views on political issues

Again using data from 1,500 voters in the CCES, the researchers also looked at dads’ views on three issues: policies “requiring schools, colleges, and universities to provide equal athletic opportunities to girls and boys”; policies “that would address the gender gap in income in the United States”; and policies to support “better enforcement [of laws] that outlaw sexual harassment in the workplace.”

Support for each of these policies was measured on a five-point scale, from “strongly oppose” to “strongly support.”

Dads with first-born daughters showed stronger support for these policies. And even when a father had several daughters, if one of them wasn’t first-born, it had no effect on their political views.

Interestingly, having a first-born daughter didn’t have an effect on the men’s views on immigration or the environment, but it did tilt them more in favor of gun control.

The researchers conclude, “It may be that just as the experience of having a first daughter awakens fathers to the importance of policies to promote gender equality, it brings greater awareness and support of measures to safeguard women against gendered violence.”

Additional coauthors on the first paper are from the University of Massachusetts.