Booker's campaign declined to comment on the departure. While O'Hern was a key staffer on Booker's Iowa team, Booker's campaign has long been seen as one of the strongest on the ground in Iowa, a state that remains a top priority for his presidential campaign.
The candidate hired some of the state's top political staffers and started organizing earlier than many of the top-polling candidates in the state. But he's struggled to gain traction in both Iowa and national polls.
A recent USA Today/Suffolk University survey of likely Iowa caucusgoers — the only one taken since the first Democratic primary debate — found Booker polling at 2% support in the state. Nationally, he fares about the same in recent polling.
That does mean Booker has met one qualification to appear at the September DNC-hosted primary debates — drawing 2% support in four qualifying national polls. But he has yet to hit the 130,000 unique donations that candidates need to fully qualify for the debate. Booker said a week ago his campaign was just 15,000 donors short of that mark.
While his campaign saw a slight drop-off in fundraising from his first quarter in the race, it announced Monday that it had raised $4.5 million in the second quarter, with $5.4 million cash on hand.