Democratic U.S. Senate Candidates Josh Turek (L) and Zach Wahls.Getty ImagesIowa Democrats on Tuesday are voting in one of the party's most closely watched primary elections this election year in a key test of the party's strategy to take control of the Senate in this year's midterms.Voters will choose between front-runner state Rep. Josh Turek and state Sen. Zach Wahls. Both are vying to become the first Democrat elected to the U.S. Senate in Iowa since Tom Harkin, who was last elected in 2008. Whoever wins the primary will square off against Rep. Ashley Hinson, a Republican who represents the state's 2nd congressional district, to fill the seat Sen. Joni Ernst will vacate at the end of this year Hinson also has a primary challenger in Jim Carlin, though she is heavily favored to win.Whoever emerges will have the difficult task of winning in a state that President Donald Trump took by 13 percentage points in 2024, and where there are nearly 200,000 more registered Republican voters than Democrats. Democrats, however, are bullish on picking up the seat as Trump's approval rating sinks amid the Iran war and the state's economy struggles.Farm bankruptcies are up across the state. Tax revenue is on the decline. And tariffs and the Iran war have hit soybean and other farmers hard. Meanwhile, Morning Consult in a poll released in May, found Trump has a -7 approval rating in Iowa, lower than in February before the Iran war began. The same poll rated the Senate race as "likely" a Republican victory.The battle between Turek and Wahls is also emblematic of a larger struggle within the Democratic Party between its more moderate and progressive wings and has become a referendum on Minority Leader Chuck Schumer, D-N.Y. The general election for Iowa Senate could be a crucial part of Democrats' push to retake the chamber. To do so, they'd need to flip four states that Trump won, like Iowa, Texas, North Carolina or Maine, while also successfully defending seats in places like Georgia, Michigan and New Hampshire."The big fight right now among the Democrats is who's more electable," Timothy Hagle, a University of Iowa political science professor, said of the Democratic primary. "Which way are we going to go? The Republicans, of course, want Wahls, because he's so far to the left that it's going to probably turn off the no-party voters. And a lot of Democrats are saying 'we need Turek because we need to have a fighting chance at this election.'"Turek is seen as the establishment candidate, with endorsements from Harkin, former Transportation Secretary Pete Buttigieg and a handful of sitting senators. Turek, who lives in Council Bluffs, on the state's western border with Nebraska, is a Paralympian who flipped a seat in the state legislature that had long been held by Republicans."I'm the only candidate in this race who has even run against a Republican, let alone beaten one," Turek posted to X in May. "I'm battle-tested and ready to take on Ashley Hinson – and win."Wahls is seen as the more progressive candidate. He's been endorsed by Sen. Elizabeth Warren, D-Mass., and has promised while campaigning not to support Schumer to lead the party if elected. He lives in Coralville, a suburb of Iowa City, which is a college town in the Democratic stronghold Johnson County."Ashley Hinson is Donald Trump's choice for this seat. My primary opponent is Chuck Schumer's choice. But this seat doesn't belong to them — it belongs to the people of Iowa," Wahls wrote in a Substack post on Monday.Iowans on Tuesday are also voting in primaries for races in three of four congressional districts and for their Republican gubernatorial candidate in a five-way race that includes GOP Rep. Randy Feenstra. Rob Sand, Iowa's state auditor, is running unopposed for the Democratic nomination for governor.