FILE -Arkansas Republican Rep. Tom Cotton (Manuel Balce Ceneta/AP, File)

Update: An earlier version of this post incorrectly characterized spending by one group. Mayors Against Illegal Guns ran ads against Sen. Pryor, not on his behalf.

Pity the poor residents of the Little Rock media market. For months, they and their fellow Arkansans been bombarded by advertisements aimed at influencing their vote in this year's hotly contested Senate race. The messages have come from an alphabet soup of political organizations on the left and right.

How thick is that soup? As of this week, 20 different organizations have run advertisements advocating either for or against the two main candidates, Sen. Mark Pryor (D) and Rep. Tom Cotton (R).

On Wednesday, the Government Integrity Fund Action Network became the latest to sponsor advertising. The conservative group, last seen running ads against President Obama and Sen. Sherrod Brown (D-Ohio) in 2012, will spend $160,000 over the next two weeks on broadcast and cable television, according to public records filed with stations on which the ads will run.

They join (take a deep breath): Americans for Prosperity, the Judicial Crisis Network, Senate Conservative Action, the National Federation of Independent Business, Secure America Now, Reclaim America, the American Action Network, the National Association for Gun Rights, Americans for a Strong Defense, Concerned Vets for America, Mayors Against Illegal Guns and the Club for Growth.

And that's just the list of groups advertising for Cotton.

Pryor's backers have spent big bucks, too. That money has come from the Senate Majority PAC, the Environmental Defense Fund, the International Association of Fire Fighters, Americans United for Change and Patriot Majority.

Oh, and Cotton and Pryor have started running ads, too. Combined, the almost $1.4 million Pryor has spent and the $820,000 Cotton has spent account for a little more than a quarter of the $8 million in television ads in Arkansas so far.

In total, Republican-allied groups are outspending Democratic backers by a margin of about $5 million to about $3.5 million.

Here's how all that ad spending looks:

(Note: "Others" includes a mix of Democratic and Republican groups)

Not all of these groups are created equal. The National Association for Gun Rights spent just $15,000 way back in April of last year, when the Senate was debating a measure to expand background checks on gun purchases (Pryor voted against the bill). The Environmental Defense Fund spent $11,000 in July on Pryor's behalf. Those two barely hold a candle to the big players on each side; Americans for Prosperity has spent more than $1.4 million on ads bashing Pryor, while Patriot Majority, a Democratic group with close ties to Senate Majority Leader Harry Reid, has spent more than $1.3 million.

The last time Arkansas voters weren't inundated by ads was during a single week-long stretch in January. Since then, it's been nothing but a steady stream of attack ads.