Columbia, South Carolina (CNN) Rick Perry has stopped paying his campaign staff, including in the key early states of Iowa, New Hampshire and South Carolina, as his candidacy struggles to generate momentum -- and cash.

The campaign's South Carolina state chairman Katon Dawson said Monday that operatives working for the campaign would no longer be paid, while Republican officials in Iowa and New Hampshire told CNN that campaign workers in both states also were notified they would not be paid. They were encouraged to stay on as volunteers, if they were able, to help Perry get through a lean summer.

The halting of pay to all campaign workers was confirmed by a GOP official.

In his second bid for the presidency, Perry has set his sights on a strong showing in the Iowa caucuses. He has spent considerable time in the state over the last three years and has a network of supporters, but his fundraising challenge underscores the difficult road ahead for a candidate in such a crowded Republican field.

The Super PACs supporting Perry's bid can foot the bill for advertising and even get-out-the-vote efforts, but are prohibited from coordinating with the campaign. And campaign staffers cannot work for the Super PAC without taking a 120-day cooling off period, under federal election law.

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