The knock felt like an encroachment. Advancing to each door proved discomforting. The experience of canvassing in Iowa in the days before the caucus felt futile.

I had the chance to volunteer for both U.S. Sen. Bernie Sanders and former South Bend, Ind., Mayor Pete Buttigieg. Nearly 70 other students and I from the Blake School in Minneapolis journeyed to the Iowa caucuses for a chance to hear candidates speak, volunteer for available candidates and view the caucusing process. Yet, over the multiple hours I spent forcing political conversations, my impact felt indiscernible.

Door-to-door canvassing has been perceived for decades as a fundamental tool for political candidates to snatch votes and cajole voters into caucusing. In the race for the nominations, candidates establish expansive on-the-ground operations to coordinate door-knocking all around states to ensure their portion of delegates. From the attempts to coerce individuals to volunteer to the production of materials for door-knockers to hand out, canvassing continues to be expansive, labor-intensive and expensive. The 2004 study "Get Out the Vote" by Columbia political scientist Donald Green and Yale political scientist Alan Gerber found that earning just one vote through door-knocking can cost up to $19. The question stands: Is it worth it?

After being furnished with training and various pamphlets by our precinct captain, I was off to knocking doors. In my shifts for both Sanders and Buttigieg, doors were seldom opened. People who opened offered hastened answers in clear attempts to shut the door without being blatantly ill-mannered. Few took a second to skim the fliers. None sustained a conversation longer than a minute. Some of the people couldn't speak English. My fellow classmates reported near-identical experiences. Granted, there are myriad factors, such as time of day and location, that affect response rates. However, the essence of canvassing — transient conversations that can feel uncomfortable for those on both sides of the door — ensures that changing someone's mind about caucusing or voting is dubious.

A 2017 study by Joshua Kalla and David Broockman published in the American Political Science Review concurs. Through analyzing 49 different field experiments, Kalla and Broockman concluded that campaign contact, like canvassing, had a net-zero persuasive effect. The only time when effects became discernible were when candidates held especially unpopular positions or spent exorbitant amounts on finding tractable voters.

The low efficacy and high price of canvassing remains pertinent. Those who donate expect their money to be put to good use. A candidate's methods for securing a voter base still concerns those who don't donate, as those methods determine success. Ultimately, more rigorous, pointed communication like town halls will provoke voter change. If voters want their candidate to control the White House, more scrupulous, cost-effective outreach methods must prevail.

Thomas Hemphill lives in Minneapolis.