DES MOINES, Iowa (AP) — Two Democrats vying to be Iowa’s next U.S. senator are scheduled to debate Thursday, as each seeks to convince voters he’s better positioned to flip the Republican-held seat in a contest that has seen heavy outside spending and high-profile endorsements. State lawmakers Zach Wahls and Josh Turek are competing in a June 2 primary. It is one of a few remaining competitive Democratic Senate primaries this year, as the party looks to find the best approach to reclaim the U.S. Senate this fall. Iowa’s Republican Sen. Joni Ernst opted out of a reelection bid, leaving the seat open for the first time since she replaced retiring Democratic Sen. Tom Harkin in 2014. Republican Senate leaders have backed Ashley Hinson, a congresswoman representing northeast Iowa, committing $29 million for her to help keep their thin majority.…