Story highlights The Sanders campaign is hiring in Iowa

The Vermont senator says organization is now the key

Ottumwa, Iowa (CNN) With just a few days of summer Senate recess left, Bernie Sanders is spending some time campaigning in the Hawkeye State.

CNN's Suzanne Malveaux caught up with Sanders following his headquarters opening in Ottumwa, Iowa. In an office filled with "Bernie" t-shirts, posters, yard signs, and some "Cats for Bernie" pins, he acknowledged that his support during what's been dubbed the "summer of discontent" has outpaced his political infrastructure.

"So what we are doing now is hiring on people. We have now dozens of people on the ground here in Iowa. Great crowds are wonderful, but that does not necessarily translate into votes. People need to be organized and know how to come out and participate in the caucuses," Sanders said.

Sanders said his campaign is not only hiring in Iowa, but also in New Hampshire and elsewhere, creating an organization structure to handle volunteers.

"We're doing it all over this country. Creating a political infrastructure with organizers, with volunteers, to make sure that supporters come out and vote. And that's how I think we're going to win this thing. We will be outspent -- let me just say this -- I know we will be outspent by our opponents. We don't have a Super PAC. We're dependent on small, individual contributors. But I think the grassroots movement that you saw out there -- that's what's going to win it for us."