HOUSTON (AP) — The third Democratic presidential debate will be held in Houston in September.

The more than two dozen candidates in the crowded 2020 Democratic primary face tougher requirements to appear in the fall debates than in the summer debates.

The Democratic National Committee is requiring participants to hit 2% in multiple polls and collect contributions from 130,000 individual donors. Only polls taken between June 28 and Aug. 28 will count.

Twenty candidates qualified for the opening round of debates in June and July. The stricter rules for the fall debate could dramatically winnow the field.