U.S. Sen. Cory Booker (D-NJ) this past weekend traveled to Florida, where he attended the Democratic County Chairs’ Retreat, fundraisers and a number of churches in advance of what experts say will be a tough 2018 general reelection campaign for incumbent U.S. Senator Bill Nelson (D-FL).

Booker implored voters to not just focus their energies on what they’re against, but in support of those causes they support. Nelson is one of 25 Democrats who must defend his seat next year, compared to eight Republicans.

In recent weeks, Booker has visited Montana, Indiana and Ohio.

Pictured: Booker, Nelson staffer Maria Lewis, Nelson, and Booker confidant Mo Butler of Mercury.