With the 2014 Senate races (mostly, except one) wrapped up, it's worth a quick dip into the murky waters of outside campaign spending to see what engorged fish were swimming around under our ... boats? (The metaphor sort of fell apart there.)

As we've noted, the 2014 elections cost $3.7 billion, a tidy sum that could not have been spent on a more worthwhile endeavor. Of that, over $600 million was spent by candidates for the Senate, according to the Center for Responsive Politics. Outside groups spent about $690 million -- both from groups that list their donors and those who don't.

To get a picture of outside spending in the Senate, we broke apart CRP data for 11 of the most tightly contested states: Alaska, Arkansas, Colorado, Georgia, Iowa, Louisiana, Kansas, Kentucky, North Carolina, New Hampshire, and Virginia. We tallied spending from non-candidate groups in those races and then ranked all of the groups that spent $2.5 million or more. Then we made a chart, showing relative spending in all races. (This includes spending both for and against candidates.)

(See correction below.)

At the top, unsurprisingly, are the two parties' Senate campaign committees. In between those is the Senate Majority PAC, a super PAC closely aligned with soon-to-be-Senate-Minority Leader Harry Reid's (Nev.) committee.

The rest of the groups are an interesting mix. There are groups like the National Rifle Association, which spent money across most of the races through two PACs. There are a number of one-off super PACs (Put Alaska First PAC, Kentuckians for Strong Leadership) that were obviously aimed at supporting one candidate in particular. Very quickly, the relative sizes of the dots drop off, as we move from the really, really big players to the really big players to the big players.

Consider a group like Planned Parenthood. One would assume that it was a major player in supporting candidates it endorsed. And, sure enough, it spent over $4 million on several of these 11 races. But on this list? It's about two-thirds of the way down, five little dots tucked in underneath all those giant ones.

In the scale of Senate campaigns these days, big spending is probably bigger than you think it is. It's simply too hard to picture the scale of sums at stake. Because the water is murky, or whatever.

Correction: Because it spent through three political groups in its advocacy, total spending by the League of Conservation Voters on the chart is lower than the group's actual spending. The group actually spent $13.6 million, largely in Alaska, Colorado, Iowa, Kentucky, and North Carolina.