The Karl Rove–backed super PAC, Crossroads GPS, has made the first major ad buy in the Massachusetts Senate contest between Scott Brown and Elizabeth Warren, attacking Warren for her support of Occupy Wall Street.

It’s no surprise that Rove and his ilk are attacking Warren. She’s a major threat to the Republican Party and its allied corporate backers for two reasons.

Number one: she’s running even with Brown in a race that may very well decide control of the Senate.

Number two: her reformist background and brand of progressive populism is deeply resonant right now. Unlike so many in Washington, she’s taken on the banks and their allies, is not beholden to them, and is not afraid of them. That makes her dangerous to the political establishment in both parties. No wonder Tim Geithner didn’t want her running the Consumer Financial Protection Bureau and Karl Rove doesn’t want her in the Senate.

Republicans are particularly afraid of her—she’s the best spokesperson the Democratic Party has on economic policy and has the potential to become one of the most popular politicians in America precisely because of her tenacity in confronting the very corporate interests who caused the economic crisis. That’s why Republicans have tried so hard to demonize her—both when she was setting up the CFPB and now that she’s running for Senate.

It’s particularly noteworthy that Crossroads is invoking Occupy Wall Street as a means to taint both the Warren campaign and the broader Occupy movement, as part of a concerted GOP backlash strategy. The ad claims that protesters at Occupy Wall Street “attack police, do drugs and trash public parks. They support radical redistribution of wealth and violence.” It distorts a quote from Warren where she said that, “I created much of the intellectual foundation for what they do,” making it seem as if Warren was responsible for lawlessness, violence and socialist-inspired chaos.

Here’s what Warren actually said in an interview with the Daily Beast:

EW: Look, everybody has to follow the law. That’s the starting point. I’ve been fighting this fight for years and years now. As I see it, this is about two central points: one, this is about the lack of accountability. That Wall Street has not been held accountable for how they broke the economy. The second is a values question, a fundamental fairness around the way that markets have been distorted and families have been hurt. I’m still fighting that fight. I’m just fighting it from this angle…I want to fight it from the floor of the United States Senate. I think that is a place to make this difference.

TDB: Is showing solidarity with them going to get in the way of that?

EW: It’s not a question of solidarity. I just don’t think that’s the right way to say it. I support what they do. I want to say this in a way that doesn’t sound puffy. I created much of the intellectual foundation for what they do. That’s the right thing. There has to be multiple ways for people to get involved and take back our country. The fight that I’m fighting now is one that is directed towards the United State Senate. That’s just how I see it.

Crossroads has pledged to spend $150 million on their campaign to take back the Senate for Republicans, so this is likely the first of many attacks on Warren. But the Rove-directed campaign against her could actually boost the Warren campaign. If the Massachusetts Senate race becomes a debate between the ideology of Rove versus the ideology of Warren, Elizabeth’s got to like her chances.