As always, anyone curious about the rubric used to determine these Daily Kos Elections Senate power rankings can see the description at the close of this piece.

Two themes emerged this month. One was the continuation of a trend that has developed as we have gone along. In the first edition of the power rankings, only eight races lacked even a single point under the criteria. By the second round, it was up to 10 races. This time around, it was up to an even dozen. One suspects that this trend may abate as we get closer to election time, if only because the volume of polling should increase to the point that, in the span of a month, lots of races will get polling attention (hell, already this month, we've seen a poll in the U.S. Senate race in Idaho.)

But the biggest theme of the month is what one could declare the "primary effect." Only a small handful of the races that made the cut for the power rankings this month came from states where the scheduled primary elections are still awaiting us in the summer months. Most either were held either in the month of May, or were held last week on Super Tuesday. With that in mind, some states with primary elections deep into the future found themselves wanting for attention, as both media outlets and pollsters honed in on the races where "the election before the election" was imminent.

The most notable example is out of the power rankings this month: Colorado. Make no mistake: this is a shocker. Not only is Colorado considered one of the real must-win races for both parties, we here at DKE actually moved it to "tossup" status earlier in the month.

So what changed from last month, when it was in the top five? The race, with no prospects of a primary, went into media hibernation. The race was practically unpolled, which is something that is guaranteed not to happen come September and October.

Thirteen other races, in addition to Colorado, managed to receive at least one point for the month of May, while failing to crack the top ten. They were (in order from closest to the top 10 on down): Mississippi (Cochran—26 points); Nebraska (open seat—25 points); Colorado (M. Udall—24 points); South Dakota (open seat—21 points); Montana (Walsh—20 points); West Virginia (open seat—16 points); Hawaii (Schatz—14 points); Oklahoma "B" (open seat—13 points); South Carolina "A" (Graham—11 points); Tennessee (Alexander—8 points); Minnesota (Franken—7 points); Virginia (Warner—6 points); Kansas (Roberts—2 points); Maine (Collins—1 point)

Of that list, the most telling (and a trifle amusing) stat is how quickly Virginia has rocketed down the charts. Remember that week or so when Warner v. Gillespie was the most talked about race in the nation? Fun times.

Looking ahead to the top 10, the one constant in this edition of the power rankings is change. Not a single state held the same position this month that they did four weeks ago. With that in mind, here are the top ten, heavily influenced (as noted above) by the recent primary elections:

#10—MICHIGAN (27 points)—DKE Rating: Leans Democratic

(Last Month: 3)

A slight surprise kicks off this month's countdown, as Michigan comes close to sliding out of the power rankings altogether. There was no clearly identifiable cause, other than a modest cooling-off in terms of pollster attention. Hell, South Dakota saw as much polling attention this month as Michigan. One possible explanation for that: There is no primary of note in Michigan, as it has been largely assumed for months that Democratic Rep. Gary Peters and former GOP Secretary of State Terri Lynn Land will square off in November. One interesting turn this month: It seems as if Peters has solidified his polling position somewhat. Looking at our polling database, we see Peters staked to a 5-6 point lead in all three polls. The biggest headline this past month was Land's bumbling performance at the Mackinac Policy Conference, which is not liable to raise GOP hopes about making this one of their top pickup chances.

#9—NEW HAMPSHIRE (30 points)—DKE Rating: Likely Democratic

(Last Month: 10)

The Granite State moves very little this month, but the presence of Scott Brown, and the media attention he seems to perpetually garner, likely ensures that this race will stay on the media radar through November. One thing that seems very unclear is that race is more deserving of that attention than several of the races below it. Polling on the race has been decidedly mixed (incumbent Democrat Jeanne Shaheen's lead in May polling ranged from 3-12 points), which might add to the intrigue. But will Brown benefit from increased attention? Consider his struggles in dealing with Obamacare, which began with that horrifically awkward moment he had in March on a home visit where he trashed Obamacare, only to be rebutted by ... his host. This race will continue to stay in the limelight, and it is an open question whether this is better news for the challenger or the incumbent.

#8—LOUISIANA (32 points)—DKE Rating: Tossup

(Last Month: 5—tie)

Louisiana is the primary example of what I would call the reverse "primary effect." While many of the top slots in the power rankings are occupied by May and June primary states, the Louisiana primary is literally not until Nov. 4 (remember the very quirky way that the state conducts its elections—it holds all-party primary elections on Election Day, holding runoffs if a candidate in a race fails to attain a majority of the vote). Therefore, as other states get polled more and discussed more around primary time, Louisiana stays in the background. Here is the numerical evidence: For the month of March, Louisiana had 30 points in our rubric. That total placed the state in third place in our inaugural round of rankings. For the past month, Louisiana totaled 32 points in our rubric—which was only good enough for eighth.

#7—OREGON (36 points)—DKE Rating: Likely Democratic

(Last month: NR)

The lone debut in the top 10 on the power rankings lies in Oregon, which was aided by both a reasonably intriguing primary, and a big news story that got the race considerable attention. Those two elements were a good news/bad news proposition for the Republican nominee, Monica Wehby. The bad news was a brief deluge of lousy headlines about Wehby's relationships, all of which hit the papers the week before her primary against state legislator Jason Conger. The good news was that, as it happens, this was not a terribly big deal. Oregon's vote-by-mail system ensured that a pretty large pile of votes were already cast before Wehby's crappy news cycles took place, and she cruised to a fairly comfortable win over Conger. Some Republicans cried foul, but one imagines that if Oregon Democrats were truly invested in this kind of an oppo hit, they'd have timed it way better than that. It would have either hit before the ballots landed in mailboxes, or closer to the general. As it is, Wehby has plenty of time to repair the damage of those headlines. Polling, however, indicates she has some work ahead of her. A pair of late May polls have her down double digits to Democratic Sen. Jeff Merkley.

#6—ARKANSAS (38 points)—DKE Rating: Tossup

(Last Month: 2)

If there was a power rankings outcome that truly surprised me, it was the slide down the charts for Arkansas. After all, the improved standing of incumbent Democratic Sen. Mark Pryor merited a shift in our race ratings here at Daily Kos Elections, as what was seen as a race leaning in the direction of a GOP pickup was reclassified as a tossup. That's worth five more points in our power rankings metric. However, the race was also substantially less polled and covered this past month. What gives? Here is a theory: I suspect the reason Arkansas was so heavily polled last month was because lots of folks rushed into the field once that first pro-Pryor poll hit, unconvinced that said poll was on point. Satisfied by multiple pollsters showing Pryor clawing back, their attention in May was diverted elsewhere. Furthermore, Arkansas, though it had a primary this month, did not have a competitive primary on the Senate side. This also likely tamped down interest this month, as big primaries elsewhere took center stage. Pryor did make some headlines this month for trying to throw Cotton on the defensive on health care, which is a bold strategy in a state where anything with the name Obama in it would seem to be anathema, but the state's Medicaid expansion has delivered health care to 150,000 residents in the state.

#5—ALASKA (41 points)—DKE Rating: Tossup

(Last Month: 9)

Alaska's presence here is a bit of a quirky one. The primary up north is still a good 10 weeks away, and there were no candidate entrances or exits of note. The race did get polled quite a bit this month, and what might have been most notable is that both general election polls showed Democratic Sen. Mark Begich with a lead over leading GOP contender Dan Sullivan. Even Sullivan's own polling put Begich ahead, in fact. In other Alaska news, Republican 2010 nominee (and 2014 candidate) Joe Miller continues to ... ahem ... distinguish himself, but polls of the primary make it clear that he is very much a third wheel in a contest that is clearly coming down to Sullivan and state Lt. Governor Mead Treadwell.

#3 (tie)—IOWA (42 points)—DKE Rating: Leans Democratic

(Last Month: 5—tie)

The Hawkeye State distinguishes itself a bit by moving up a few slots into the top echelon of Senate races. It was a consistent performance: mentions in roughly half of the Daily Digests this month, coupled with a handful of polls (three of the primary, and a pair for the general), that pushed Iowa into the top three. One might expect, however, that this position might soften next month, since Republican Joni Ernst's decisive win in this week's primary might put the race into a momentary stall ("breather" might be a better word). Ernst's thumping came despite (or, perhaps, given the conservatism of a primary electorate that embraces the likes of Steve King, because of) a rather interesting performance in one of the final debates of the primary. Ernst now must gear up for a general election in which she will challenge veteran Democratic Rep. Bruce Braley.

#3 (tie)—NORTH CAROLINA (42 points)—DKE Rating: Tossup

(Last Month: 1)

After two months as the belle of the electoral ball, North Carolina cedes the top spot in the power rankings. Of course, the race is still arguably the closest race in the nation, and that did not change in May. So what's changed? Well, nothing, really, save for the fact that the GOP primary is over. Thus, the race has headed into a tiny bit of a holding pattern. It's still a big one—only two races were polled more often (the two ahead of them in this month's rankings). But, absent daily updates on the GOP primary (and a raft of polling), the gigantic level of coverage in North Carolina tapered off. Despite that, it still ranked in the top five, where I'd be legitimately surprised if it didn't remain through November.

#2—KENTUCKY (50 points)—DKE Rating: Leans Republican

(Last Month: 8)

One of the biggest movers this month was the Bluegrass State, in part because the state held primaries this month, but also because there is a growing sense that McConnell is not putting this race away, by any means. Not everyone shares that sentiment (a couple of forecasters give McConnell up to a 97 percent chance of victory). Personally, if any of those folks want to give me 32-to-1 odds, I'll be happy to place my bets with Alison Lundergan Grimes. We here at Daily Kos Elections agree that the race is not yet a tossup (hence, our "Leans Republican" rating), but McConnell is not out of the woods, especially now that he seems to have hacked off popular Gov. Steve Beshear enough on the health care issue that Beshear has jumped off the sidelines and fired back at McConnell. The state's terrain sucks for Democrats in general, but polls keep showing a competitive race.

#1—GEORGIA (72 points)—DKE Rating: Likely Republican

(Last Month: 7)

Georgia, without question, is the beneficiary of the "primary effect." The state's coin-flip Republican Senate primary and the ensuing runoff, received a ton of attention. Not only did we see mentions in the Digest more than two-thirds of the time during the month of May (15 out of 21 days), but the Peach State set a new single-month record for the number of polls conducted (13!). The only thing we didn't see this month was a ratings change, but that could also be in the future, if Democrat Michelle Nunn can stay in a strong poll position, and the GOP runoff between Perdue and Kingston turns nasty. That hasn't happened yet, but one thing a lot of people have forgotten: There is a ton of time between now and the runoff. The Georgia GOP runoff is scheduled for July 22.

