It may be vacation season for most Americans, but not for those who are running for office in this year’s mid-term elections — or for those who want to influence the outcome of those races.

Sunlight’s Ad Hawk, a tool that helps voters identify the people and the interests behind the political advertisements bombarding their living rooms, has had a particularly full in-box this week, picking up new ads in several of this year’s key Senate races.

Crossroads GPS, part of the GOP political spending combine that told the Associated Press it plans to spend $20 million this fall in six key Senate races, has uploaded ads for two of them:

In Arkansas, where Sen. Mark Pryor is in a tight re-election battle, Crossroads has posted an ad emphasizing the two-term Democrat’s ties to President Barack Obama, who got just 37 percent of the vote in Arkansas the last time he was on the ballot.

Arkansas is one of the states where Crossroads appears to have been most active, according to ad buys compiled by Sunlight’s Political Ad Sleuth from records filed by the state’s TV stations with the Federal Communications Commission. You can see the Crossroads buys in Arkansas here.

In Colorado, home of another one of this year’s most vulnerable Democrats, Mark Udall, Crossroads is attacking the first term senator for being insufficiently supportive of the controversial Keystone XL pipeline, which proponents see as a job-creator and opponents see as an environmental disaster.

Both ads deliver highly negative messages about the politicians they are targeting but because they never explicitly call for a vote against them and because they are airing well before the 60-day pre-election window when the Federal Elections Commission requires such messages to be reported, expenditures on the ads don’t have to be reported either. But enterprising watchdogs can crack open the contracts on Ad Sleuth and enter the numbers into a database that Sunlight has created. The Crossroads buys in Colorado are here.

On the other side of the environmental debate, the big-spending League of Conservation Voters has posted two new ads attacking Joni Ernst, the Republican candidate vying for an open Iowa Senate seat. Both portray Ernst as “too extreme” for the state, and one links her to GOP firebrand Sarah Palin and the conservative bankrollers Charles and David Koch.

The League of Conservation Voters’ ad buys in Iowa can be viewed here.

Airtime in Kentucky, where Senate Republican Leader Mitch McConnell’s reelection bid has set off a barnburner of a contest, has been a hot commodity since early 2013, Political Ad Sleuth records for the Louisville market show. Ad Hawk this week picked up two new ads in the race, one from McConnell’s Democratic opponent, Alison Lundergan Grimes, and another from the Kentucky Opportunity Coalition, a dark money group that’s backing McConnell.

Finally, the U.S. Chamber of Commerce has posted an ad strongly backing Rep. Jack Kingston in the July 22 runoff for the GOP Senate nomination in Georgia. Kingston faces businessman David Perdue. Details on the Chamber’s ad buys in the Peach State are available here.