This is the second burst of ads from the group targeting Democrats in Missouri, Massachusetts, Montana and Nebraska, hitting airwaves one month after an initial round where Crossroads spent almost $2 million in those states and another $2.6 million to attack Democrats in five swing states.

The ads, which will air for two weeks, lambaste Democrats for spending recklessly and allowing the national debt to escalate, and work to tie the candidates to an unpopular President Obama.

“Look at the damage he did: higher taxes, cutting Medicare spending, embarrasing Nebraska. Ben Nelson sold out to Obama when it counted most," says one of the ads.

Crossroads will spend almost $123,000 attacking Sen. Ben Nelson (D-Neb.), who hasn’t yet announced whether he will seek reelection. Another $251,000 will go to ads targeting Sen. Claire McCaskillClaire Conner McCaskillGovernment watchdog finds safety gaps in assisted living homes GOP Senate candidate fundraising lags behind Dems in key races McCaskill challenger links human trafficking to 'sexual revolution' of 1960s MORE (D-Mo.) by portraying her and Obama as one and the same. In Montana, the group will spend $136,000 hitting Sen. Jon TesterJonathan (Jon) TesterDemocrat Manchin: Pence attacks prove ‘they don't want bipartisanship’ in Trump admin Tester invited the Border Patrol Union’s president to the State of the Union. What does that say to Dreamers?   These Democrats will have a hard time keeping their seats in 2018 MORE (D).

But the biggest buy is saved for Massachusetts, where Crossroads has made Democrat Elizabeth WarrenElizabeth Ann WarrenGovernment watchdog finds safety gaps in assisted living homes David Crosby: Shared dislike for Trump could reunite Crosby, Stills, Nash and Young Dem senators tell Trump he doesn’t have ‘legal authority’ to launch preemptive strike on North Korea MORE a top target of its 2012 election efforts. The group will spend $524,000 to undercut Warren in December.

“Tell Professor Warren: We need jobs, not more bailouts and bigger government,” the Massachusetts ad says.

The behemoth of outside spending for the 2012 cycle, Crossroads GPS, together with its affiliate, American Crossroads, has already dropped more than $20 million attacking Democrats and Obama this year.

From both sides of the political divide, outside groups have unleashed more than $35 million to influence election results, according to a recent investigation by The Hill.

Watch the ads: