That’s important for campaigns because it could have consequences for the effectiveness of such work; canvassing was a major focus for both Democratic and Republican campaigns, as well as outside groups, in the 2014 elections. Although the study does not assign a cost to mismatching volunteers with voters, it suggests that campaigns could better utilize their volunteers to reduce the risk that they inadvertently turn voters away.

“The most liberal people — young, from out of state — are the ones who are spending their time out knocking on doors,” Mr. Enos said in a telephone interview. He described seeing many of his own government students from Harvard volunteer for field work in the Obama campaign in blue-collar or inner-city areas in other states. The Obama campaign at times encouraged volunteers to veer from the scripts it provided for such interactions, which may have resulted in volunteers’ own interests superseding those of the campaign.

He said campaigns might not be thinking about the full range of volunteers available. “Older volunteers are at the office entering data” when some of them might be better matched with voters more like them, he said.

Although the paper looked only at Obama campaign volunteers, there are implications for other campaigns and parties. The authors conclude that parties and campaigns tend to attract highly ideological volunteers who are driven mainly by a single issue like health insurance or abortion rather than broader issues like the economy or education. Midterm elections, which don’t have the broad appeal of a presidential election, might even exacerbate this condition because they tend to attract partisan loyalists.

The authors got permission from the Obama campaign to have their survey of ideology randomly appear as part of the software that volunteers used when contacting voters. The survey was taken by 3,095 volunteers, some more than once, and showed that “Obama’s 2012 campaign workers were extremely liberal, even relative to strong Democrats who match the observable demographic profile of the workers.”

Mr. Enos said the imbalance most likely extended to Republican campaigns as well.