America's fastest-growing religious group is also one of the hardest — and costliest — to reach: the "nones." Why it matters: Religiously unaffiliated Americans now make up a large and growing share of the electorate. But without church-based networks, they're significantly more expensive for campaigns to reach and mobilize. "Nones" are geographically and socially dispersed. Campaigns must rely on costly digital ads, canvassing and persuasion to reach them. By the numbers: A record 29% of Americans now identify as religiously unaffiliated — the largest single religious cohort, surpassing Catholics (19%) and evangelical Protestants (23%), per Pew Research Center . Among Gen Z , it's even higher: Roughly 4 in 10 adults ages 18–29 are unaffiliated, according to the nonpartisan Public Religion Research Institute (PRRI) . About one-third of Democrats and independents identify as nonreligious, vs. roughly 13% of Republicans, per PRRI .…