Pryor raised $1.9 million, making his the largest fundraising haul so far of Democrats facing tough reelection prospects next year. It's especially impressive since he hails from a small, poor state where fundraising dollars are hard to come by.

That number was boosted significantly by a fundraiser with Clinton early in the year that brought in $1 million. He now has $3.4 million in the bank.

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Republicans don't yet have a candidate, though national Republicans are hopeful Rep. Tom CottonThomas (Tom) Bryant CottonLawmakers introduce bill to block U.S. companies from doing business with Huawei Five things to know about Iran's breaches of the nuclear deal Hillicon Valley: Trump gets pushback after reversing course on Huawei | China installing surveillance apps on visitors' phones | Internet provider Cloudflare suffers outage | Consumer groups look to stop Facebook cryptocurrency MORE (R-Ark.), a freshman and favorite of both Tea Party groups and national security hawks, will jump into the race. Cotton is also a fundraising powerhouse, making Pryor's haul even more important.