Pryor is, according to an announcement issued by SCF Executive Director Matt Hoskins, the group's top target in 2014.

An SCF source indicated both his vulnerability — Pryor is running for reelection in a state that President Obama lost by more than 20 percentage points in 2012 — and interest from grassroots members in his defeat encouraged the group to set him in its crosshairs as a top target this cycle.

The radio ad, which is backed by $35,000, according to an SCF source, is part of an extended educational campaign that will amount to "10 times that or more" to educate voters on Pryor's record.

It features a man and a woman discussing whether a couple could agree "95 percent of the time," and noting that Pryor "voted with Barack ObamaBarack Hussein ObamaThe Hill's Morning Report - Trump seizes House impeachment vote to rally GOP Democrats warm to idea of studying reparations Trump blasts minority Democrats, rally crowd chants 'send her back' MORE 95 percent of the time."

The ad highlights his votes for the stimulus, for Obama's healthcare overhaul, the Wall Street bailout, and charges that he "voted to use taxpayer money to fund Planned Parenthood, the nation's largest provider of abortions."

And it directs listeners to, where supporters can sign up to receive more information. SCF is hoping to build a "massive" email list of supporters from the email to keep active throughout the race, according to an SCF source.

It's an early look at what's likely to be the roadmap for any Republican running to defeat Pryor in an increasingly red state. Though he ran without Republican opposition in 2008, Pryor will face heavy attacks this cycle from groups like the Senate Conservatives Fund and the Club for Growth, which also targeted him with its first ad of the cycle in late February.

No Republican has yet announced an interest in the seat, but 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.), who is considering a bid, would be likely to get the support of the two groups, which are known for backing anti-establishment candidates.