If this month has been a giant, delicious cake layered with all of Hillary Rodham Clinton's favorites, then Monmouth University just slathered on a whole lot of icing. Its new poll puts Clinton up 41 points in Iowa — the widest lead she's seen there in any poll since June. Or: since before the Bernie Sanders surge.

It's a lead so big that it is worth raising an eyebrow and holding at arm's length, in the manner of a stereotypical movie detective. Hmm, one might say, turning it this way and that. Hmmmm.

It's a good time to go back to the polling average compiled by Real Clear Politics. In an average of recent polls, Clinton is up in Iowa by a more modest 15.5 points — still more than enough to inspire a few high fives around the office in the manner of a stereotypical successful political campaign.

Let's take the poll at face value. How could Clinton have gone from being up 11 in Quinnipiac's poll just last week to 41 now?

We noted for a long time that we expected Clinton to benefit from the departure of Joe Biden; the two shared a large base of support. If you look at the trend in Iowa over the course of the month, Clinton was already gaining steam even before Biden bowed out. Now that he's gone, it's not surprising she would surge even further ahead. (We've included a "Biden+Clinton" line as a sort of guidepost of what we might expect Clinton to see if Biden's base was 100 percent shared with her — which is an overestimation of what she'll actually get but is still instructive.)

In the new Monmouth poll, Clinton leads with men by 22 percent and with liberals by 23. Both are areas in which she had been doing worse against Sanders.

What's more, Clinton backers are far more likely to have made up their minds than Sanders backers — or than Democrats and Republicans on the whole.

The Monmouth survey makes very clear that there has been no Martin O'Mentum. The majority of Clinton backers would go to Sanders if she dropped out, and vice versa.

It's also worth noting that Clinton's current lead in the polling average is far higher than at any point in 2007. This race will likely tighten again, but the picture painted in 2015 is very different than what we saw before Clinton lost to Barack Obama. That year, Iowa was a dogfight. This year, Clinton plunged — but has bounced.

To be fair, this is the sort of poll that campaigns actually hate. Clinton needs to show donors and volunteers in Iowa that there's a reason to keep donating and fighting and donating. Having people think she's up by a million miles doesn't help that effort.

Or, put another way: Too much cake can make you sluggish and sick.