Bloomberg just released a national poll that shows Trump still in the lead with 24%, Carson in second with 20%, Rubio in third with 12%, and Cruz in fourth with 9%. No one else gets a level of support worth mentioning.

This is continuing a trend that we have seen slowly develop basically since the second debate. The race has come down to basically four candidates. Trump and Carson remain in the lead, but their combined share of the GOP primary electorate has been slowly sliding from its high water mark of 52% in the middle of September to its current level in the mid-40s. Rubio and Cruz have benefitted partially from the  continued implosion of Bush and the fade of Fiorina, but also the slow erosion of the Trump/Carson contingent.

A couple of factors conspire against the possibility of either Trump or Carson maintaining a national lead through the Iowa Caucuses. First, the caucuses are almost a full month later in this election cycle than they were in 2012. In 2012, they were held on January 3rd, when people had barely polished off the last of their Christmas turkey. This year, they will be held on February 1st, which means that voters will get an extra month during the actual election year to ruminate over their choices.

As much as we here in the blogosphere obsess about these things starting in about March of the year prior to a Presidential election year, the vast majority of the voting public does not tune in seriously until January of the actual election year itself. This means more time for the fundamental unseriousness of the Trump/Carson campaigns to really sink in.

The second and more important factor is that this campaign is increasingly turning into more of a foreign policy centered campaign, an area in which both Trump and Carson have exhibited humongous gaps in their knowledge – and more importantly, in their willingness to even learn.

Carson’s difficulties with foreign policy are well documented at this point, to the extent that his own advisers have begun grousing publicly about how he’s not only unprepared but also unwilling to learn. After all, you don’t have to have extensive background knowledge of the region to know that China is not acting in Syria right now; you just have to watch the news sometimes. Carson’s supporters have forgiven him a lot in these early months, expecting that he can learn on a curve, but as the media is pretty much camped out in Paris over the last week carrying live shots of humongous explosions as French police conduct raid after raid on ISIS safe houses, and ISIS continues to release threats against NYC, you have to expect that Carson’s grace period has likely come to an end.

Trump, for his part, is louder about national security, which is persuasive to the low-information voters he feasts on, but it makes his gaps and gaffes all the more magnified:

The real estate mogul has raised plenty of eyebrows with his statements on foreign policy matters: by promising to seize oil from enemies in the Middle East; suggesting China is a party to the Trans Pacific Partnership trade deal; and proposing that fighting ISIS be left to Russia, a stance on which he has this week begun to evolve.

Who is formulating these positions? From all indications, it is Trump himself.

It has been months since the billionaire businessman first promised a forthcoming rollout of his national security team — a rollout that has not yet occurred. Asked by RealClearPolitics this week when the campaign plans to announce its advisers on national security or foreign policy, Trump spokeswoman Hope Hicks responded: “We don’t have anything to share at this time.”

The delay might be due to the fact that there is still no team to announce.

Trump’s supporters have long claimed that there is nothing more important than showing the GOP Establishment who is boss, but watching one of the foremost cities in Western civilization reduced to a war zone on live TV has a way of putting that theory to the test that all the fighting in Syria has not. For all that people might have strongly sided with either Rubio or Paul in the last debate, both at least have a foreign policy worldview that doesn’t come from the back of a cereal box.

The gap between the “protest candidates” of Trump and Carson on the one hand and Rubio/Cruz on the other shrinks every time a poll is released. The more serious the news becomes, the likelier that is to continue.