Former Virginia Gov. Tim Kaine’s Senate campaign has started using Rootsquare—a fundraising app that runs through Facebook—to engage online supporters and donors.

The app lets friends measure their campaign and fundraising efforts against those of other users. They can then use the app to boast their support for the candidate on their Facebook news feed and encourage Facebook friends to engage with the campaign.     

For now, the Kaine campaign is using RootSquare to engage with a targeted group of online supporters, according to a release sent by the campaign Wednesday. It’s first promotion: “Harmonica with Tim.” One lucky supporter not only wins a dinner with the former governor and DNC chair, but they’ll also get a harmonica lesson from Kaine. As the Washington Post notes, videos displaying Kaine’s harmonica skills abound on YouTube.   

Rootsquare debuted in the political world last spring—it was used by David Chiu’s San Francisco mayoral campaign. Currently, Kaine’s campaign is the only federal campaign using the app.