-- Your code
create table fg_180512_interactors_matches_party distkey(matched_id) sortkey(matched_id) as
select
    democrats.fg_180512_interactors_matches_2.matched_id, -- Use an alias, a in this instance.
    source_id,
    score,
    LEFT(b.vb_vf_voter_status,1) as vb_vf_voter_status,
    LEFT(b.vb_vf_party,1) as vb_vf_party,
    ROUND(b.ts_tsmart_partisan_score) as ts_tsmart_partisan_score
from democrats.fg_180512_interactors_matches_2 a
left join ts.ntl_current as b using (matched_id) -- Matched id doesn't exist in ts.ntl_current, so you can't join on this column.
-- See below for example of a.key = b.key

-- Working code...
create table fg_180512_interactors_matches_party distkey(matched_id) sortkey(matched_id) as
select
    matched_id, --removed schema designation
    source_id,
    score,
    LEFT(b.vb_vf_voter_status,1) as vb_vf_voter_status,
    LEFT(b.vb_vf_party,1) as vb_vf_party,
    ROUND(b.ts_tsmart_partisan_score) as ts_tsmart_partisan_score
from democrats.fg_180512_interactors_matches_2 as a -- Added an alias, use this instead of a full table/schema name.
left join ts.ntl_current as b on a.matched_id=b.vb_voterbase_id

-- Aliases, here is a basic example.
select
	a.primary_key -- You are grabbing the column from table1
	b.first_name -- You aer grabbing the column from table2
from schema.table1 as a
left join schema.table2 b on a.primary_key = b.primary_key