UPDATED: 3:25 p.m. |  The Senate Majority PAC launched a $1.5 million digital advertising campaign targeting vulnerable Republicans up in 2016, the group told Roll Call on Thursday.  

The first advertisements will begin appearing in Pennsylvania against Republican Sen. Patrick J. Toomey on Facebook , Twitter and the massive Google ad network used by many websites. “The Republican agenda puts special interests and partisan ideology ahead of what’s best for everyday Americans and Pat Toomey is the poster boy for those misplaced priorities,” said Shripal Shah, a spokesman for Senate Majority PAC.  

The Pennsylvania digital ads — the first installment in the group’s 2016 digital effort — ask, “Who’s Pat Toomey Really Working For?” and link to a report that accuses him of voting along the lines of one of the Democrats’ favorite boogeymen — the billionaire Koch brothers.  

Steve Kelly, a spokesman for Toomey’s campaign, took issue with that depiction.  

“The Allentown Morning Call said it well when it wrote, ‘Pat Toomey puts principles over party-line obedience’– whether it’s on background checks for gun purchases, job creation, or keeping predators out of schools, Pat is proud of his work across party lines to make our communities safer and our economy stronger,” Kelly said. “Suggestions to the contrary are nothing but election season political attacks.”  

Toomey is one of the most vulnerable Republicans seeking re-election. Despite a crowded Democratic field, the Pennsylvania Senate race is rated Tilts Republican by the Rothenberg & Gonzales Political Report /Roll Call.  

Shah said the $1.5 million budgeted for the digital program, which could change later in the cycle, is similar to what the group spent in 2014. He added that ads in other states will begin soon.