By winning the Democratic primary on Tuesday, Newark Mayor Cory Booker is now a shoo-in for the New Jersey seat of the late Sen. Frank Lautenberg. Democrats should be elated that one of their rising stars, a popular mayor with 1.4 million followers on Twitter and a big media presence, is likely getting a promotion.

But along his precipitous rise to becoming one of the few African-Americans ever elected to the U.S. Senate, Booker has lost the support of the left wing of the Democratic Party. In fact, many liberals are downright gloomy about his impending ascension. (His Republican opponent in the Oct. 16 special election is right-wing tea partier Steve Lonegan.) 

“He will, in short, be the worst kind of senator,” wrote Salon’s Alex Pareene in a column Tuesday, begging New Jersey voters to support one of the other Democrats in the race and casting Booker as someone who is out to promote himself, rather than champion issues. Citing Booker's close ties to Wall Street and Silicon Valley, Pareene calls him “the worst sort of Democrat, and Democrats should be doing everything in their power to wrest control of the party away from people like him.”

Following Booker’s landslide win, where he outpolled three opponents combined, The New Republic displayed an article on its home page titled “Cory Booker Is Even Worse Than His Critics Say.” Noam Scheiber described the mayor’s worldview as believing that “the economy functions best when wealthy people are allowed to deploy their capital freely, and that progress ensues when they train some of their gains on society's ills.”

That Booker is good friends with heavy hitters on Wall Street and in Silicon Valley is well-documented. Most famously, Booker lost progressives' trust in May 2012 when he broke with President Barack Obama’s campaign message to defend private equity capitalists like Mitt Romney. Booker later walked back his remarks, but for progressives, the damage was done. Then, during his Senate campaign, Booker flirted with the idea of cutting Social Security benefits, only to back off after progressive groups slammed him.

That hardly means that Booker’s political future, and perhaps eventual presidential aspirations, are over. If anything, progressives might be more nervous about a Sen. Booker than he is about them. As Scheiber noted in his piece, Booker’s is "the worldview that already dominates Washington." But it does put him at odds with the recent rising stars of the Democratic Party who have sung a more progressive tune, people like Massachusetts Sen. Elizabeth Warren, San Antonio Mayor Julian Castro and his twin, freshman Rep. Joaquin Castro, and even more recently, Texas state Sen. Wendy Davis.

The tensions between the more conservative and liberal wings of the Democratic Party have been ongoing for years and are unlikely to subside. But after progressives notched some notable wins in the 2012 election with Warren, as well as Wisconsin Sen. Tammy Baldwin and other recent candidates, Booker appears a win for the other side.