Rep. Rush Holt (D) is out with a new ad in the New Jersey special Senate election in which he says Cory Booker "is no progressive."

But what's perhaps most notable about the ad is that it's the first TV ad in which anyone attacks Booker.

With the all-important Democratic primary for the seat of the late senator Frank Lautenberg (D-N.J.) just eight days away, there is little reason to believe Booker is in anything resembling a close race.

And even as Booker has shown a large lead in every public poll of the race, his opponents haven't been able -- or really even attempted -- to lay a glove on the rising Democratic star.

Up until Holt's ad, the attacks on Booker were pretty much relegated to inside baseball arguments about his refusal to take part in certain debates or sign a so-called "people's pledge," along with a little innuendo about how he's a flashy candidate rather than a substantive politician. A new conservative super PAC went up with a small ad buy on the Web, but Democrats have been pretty hands-off.

And even as some -- including the New York Times -- have questioned Booker's tenure as mayor, Booker's opponents have yet to come close to using that against him.

Rep. Frank Pallone, the well-funded House member who was supposed to be Booker's biggest obstacle, has barely mentioned Booker, playing up his own credentials and the support of Lautenberg's family rather than directly attacking Booker.

Holt also has run a largely positive campaign, focusing on his own progressive bona fides and his status as the guy who beat the Jeopardy! computer, Watson.

In the end, Booker's biggest break of all might have been the short window for the special election. With basically two months from the date the special election was called until the primary, it's difficult for a little-known House member to build the kind of support base he needs and land some punches on Booker.

We have yet to see a poll in the last two weeks, but there's little reason to believe Booker's 30-plus-point lead will show any signs of abating.

There is a major debate being held tonight at Montclair State University, but unless Booker really steps in it, it's hard to see how he doesn't win the primary and enter October's special election as a prohibitive frontrunner against likely GOP nominee Steve Lonegan.