Sen. Mark Kirk (R-IL) has been working overtime to convince voters he’s a genuine independent voice in the Senate. The vulnerable incumbent’s Democratic opponent Rep. Tammy Duckworth unleashed a storm of tweets to show just how often he’s been in lockstep with his party. 

Sen. Kirk of Illinois would really like voters to believe that he makes decisions independently of his party. He recently called for a vote on Supreme Court nominee Garland and has criticized North Carolina’s new anti-LGBT law HB2.

There’s evidence, though, that these actions are really just election-year theater rather than genuine party-bucking. Earlier this month, Kirk told Roll Call that he thinks everyone in his party “understand[s] that I have to be separate from the leader,” since Illinois leans Democratic. He also cozied up to extremist Bush administration “diplomat” John Bolton at a recent fundraiser.

Even so, he’s been pushing the line that he’s always been a genuine independent, telling Politico on Thursday that he’s “just Mark Kirk being Mark Kirk, because I was always very independent of my party in the House, as well as in the Senate,” adding that he’s “not just a party xerox.”

Not content to let that claim stand, his opponent took to Twitter to respond. Unleashing a storm of tweets under #SenatorXerox, Duckworth listed a number of ways in which Kirk was in lockstep with his party’s leadership, including the announcement  that he’d support Trump, his efforts to shutdown the government in opposition to ObamaCare, and his opposition to the paycheck fairness bill.

It’s not the first time Duckworth has taken to Twitter to expose Kirk’s hypocrisy, and it probably won’t be the last.