There sure is, says Marc Thiessen. Matt Lewis made the same point more than a month ago, noting that that unbelievably shoddy Reuters hit piece in January wasn’t the only story questioning Rubio’s past to bubble up in the national media lately. Go figure that Democrats would be anxious to torpedo “the conservative Obama” before he lands on the ticket and becomes a mortal threat in 2016 or 2020.

In the Headlines thread on Thiessen’s piece, Steven Den Beste comments, “God knows, we wouldn’t want to have anybody in the Executive branch who hadn’t been fully vetted by the press!”

In recent months, a whispering campaign has spread in Washington suggesting that Rubio may look good on paper, but he cannot “pass vet” for the vice presidential nomination. The whispers became more audible last October following a hit piece by Washington Post reporter Manuel Roig-Franzia, who accused Rubio of deliberately “embellishing” his family history by saying that his parents arrived in the United States after Castro took power when they, in fact, arrived during the Batista years. (I pointed out at the time that the story offered zero evidence that Rubio intentionally misled anyone).

Then in February came the revelation that when Rubio was 8 years old and living in Las Vegas, his family was baptized into the Church of Latter-day Saints and attended a Mormon church for a few years before returning to Catholicism. Rubio’s detractors pounced, ridiculously arguing that this disqualifies him from serving as Romney’s running mate, because conservatives would never accept an “all Mormon ticket.”…

The Great Whisperer has used these stories to plant seeds of doubt about Rubio: How well do we really know this guy? What else is there in his record? Indeed, the whispers are making their way into the mainstream commentary. Even in ranking Rubio first on his vice presidential list, The Post’s Chris Cillizza writes, “We hear whispers that his time in the state legislature could be mined by a good opposition researcher.” And this month, the National Journal downgraded Rubio’s position on its vice presidential power rankings because, it claimed, Rubio “skated into office without much of his past being vetted in the media. That would change in a hurry if he’s tapped for the vice presidency, and coming four years after Sarah Palin had such trouble adjusting to harsh scrutiny, that’s a very real concern for some Republicans. After all, Tallahassee has its own secrets.” (Miami Herald political reporter Marc Caputo vigorously disputes the suggestion that Rubio was elected without proper scrutiny by the Florida press corps.)

Roig-Franzia, the WaPo reporter who broke the story about Rubio’s family, has a biography of him coming out in June that’s bound to be brimming with Democratic oppo research. As Thiessen notes, that’s one reason Rubio’s rushing out his own book — to beat his enemies to the punch in defining his image. But it’s not the only reason: Read this timely Tampa Bay Times piece noting that a lot of the moves Rubio’s made lately, including hiring his own oppo research team to make sure there are no skeletons in his closet that he’s unaware of, look like the maneuverings of a guy who’s preparing to join a national ticket. Two questions, though. If the economy grows the next two months and unemployment drops, would Rubio want to be on a ticket that suddenly looks like it’s a longshot against The One? He’s a polished speaker and has spent more than a year in the Senate getting up to speed on national policy, so he’d acquit himself well on the trail regardless. Even in a losing effort, the increased national exposure would make him a top-tier candidate for 2016. But there is a stigma in losing, and that stigma would be significant if Romney/Rubio ended up underperforming among the Latino voters whom Rubio’s supposed to deliver. He’s going to be a top-tier candidate in 2016 whether he’s on the ticket or not. Why take the risk in joining it?

Two: Are we sure it’s Democrats and liberals who are exclusively to blame for the whispering? There are a lot of young, ambitious Republican governors and legislators out there eyeing this guy as a huge obstacle to the nomination for them down the road. In fact, arguably it’s his Republican rivals, not the Democrats, who have the most to gain by dropping oppo on him now. If the Dems have something big in the pipe, they’re better off letting Romney put him on the ticket and then feeding it to the media. For Republicans, though, the time to derail Rubio is before he joins the ticket and instantly becomes a presidential-level star. That’s not to say the left isn’t responsible for some or most of the hit pieces appearing in the media food chain, but I’d be surprised if they’re responsible for all of it.