A Senate primary in Iowa has unexpectedly emerged as the nation’s clearest test of the Democratic rank-and-file’s anger at party leadership, with a leading candidate hoping that biting critiques of Senate Minority Leader Chuck Schumer (N.Y.) can counteract big money backing his opponent.

State Sen. Zach Wahls, who was long seen as the frontrunner in the race, is trying to battle back against $5 million spent by VoteVets, a super PAC that typically backs Democratic veterans, in support of state Rep. Josh Turek. The race, which is taking place amid a wave of optimism among Iowa Democrats who believe the state’s working-class voters are fed up with sluggish growth, could determine whether the party can turn the reliably red state into a battleground and create another pathway to win back control of the Senate.

“I do not think we are going to win in November if we can not be honest about the need for new leadership for our party in Washington, D.C.,” Wahls said in an interview. “And that starts with Senator Schumer.”

Wahls has said repeatedly he believes the party should move on from Schumer’s leadership, while Turek has been publicly neutral on the issue. Schumer has not officially endorsed Turek, but D.C. leaders’ preference for him is a poorly kept secret. Turek, they believe, is the better choice to win in November because of his inspiring personal story — he was born with spina bifida and won two gold medals in wheelchair basketball as a Paralympian— and his history of victories in territories President Donald Trump won.