In politics, the unthinkable must be thought about.

Not all that long ago, it was unthinkable that Hillary Clinton could lose Iowa, the first of the 2016 presidential contests.

True, she had lost the Iowa caucuses in 2008, coming in a shocking third after both Barack Obama and John Edwards.

And she had had everything going for her. She had the money, she had the endorsements, she had the name recognition, and she had the demographics, i.e., there are virtually no black people in Iowa, so how was Barack Obama supposed to beat Hillary Clinton there?

Obama’s people were astonished at how lightly Hillary’s people were taking Obama.

“The crowds he was drawing in 2007 should have scared the shit out of them,” Bill Daley, who had run Al Gore’s presidential campaign in 2000 and had been Bill Clinton’s secretary of commerce, told me. “They should have been asking: ‘How do you take this guy out?’”

Instead, the Hillary people were vigorously fighting with each other, knifing each other in the back when they were not too busy knifing each other in the front.

Daley thought the Clinton campaign wildly underestimated Obama, in part because of his race. “He’s black, start there,” Daley said. “When was the last time a black guy pulled this off? Well, never. A black guy in the Senate only three years, who had never done anything in their opinion? They felt he was just a pretty boy. They had a bloated campaign and no strategy.”

“Hillaryland was about Hillary,” Daley said. “By the time they focused on [Obama], it was over. He was credible, he was real, and they couldn’t stop him.”

And it was Iowa that made Obama credible and real.

“If I win the Iowa caucuses,” Obama told Daley early in 2007, “I can get the nomination.”

Could an Iowa victory catapult Bernie Sanders to the same kind of credibility and stature that Obama received from his victory there? And could Sanders possibly beat Hillary in Iowa?

The Hillary Clinton campaign doesn’t think so.

Bernie Sanders? Please. It is to laugh. This guy is no Barack Obama.

Sanders is a 73-year-old “democratic socialist,” whatever that is, born in Brooklyn and registered as an independent in his home state of Vermont. This is the first time he has run in a Democratic primary. He is also Jewish, another group that is that is a little scarce in Iowa, which has a grand total of about 6,170 Jews or about 0.2 percent of the state’s population.

By contrast, whenever Hillary Clinton comes to Iowa, she likes to say: “I grew up in a middle-class family in the middle of America.” She is mainline Protestant (United Methodist) in a state where mainline Protestants are a 25 percent plurality of voters.

She also has the invaluable experience of having organized Iowa once before, while Sanders has never run in Iowa.

Iowa should be a walkover for Hillary, a breeze, especially since her campaign has rolled out the new Hillary 2.0, which repairs the minor imperfections she sometimes showed while campaigning in the past.

Like how she doesn’t really like campaigning.

As Katie Glueck of POLITICO wrote on Aug. 16 during Clinton’s visit to the Iowa State Fair: “While Clinton is notorious for avoiding big crowds, she walked around the fairgrounds talking to anyone who approached her or asked to snap a picture.”

Stop the presses! Hillary talks to people! Read all about it!

I would say a presidential candidate who is “notorious for avoiding big crowds” is a presidential candidate who is in the wrong business. Running for president is often about talking, meeting with and winning over big crowds, the bigger the better, in fact.

But who is attracting the big crowds this time around? You guessed it: Bernie Sanders.

He draws very, very big crowds. In Los Angeles in mid-August, Sanders drew a crowd of 27,500 people, which The Washington Post pointed out was “about five times as large as any crowd that has turned out for Democratic front-runner Hillary Rodham Clinton.”

This was not good news for Clinton, but the real body blow came this weekend: The highly respected Iowa Poll came out and for Clinton -- the news ran from bad to worse. The poll said:

“Clinton has lost a third of her supporters since May, a trajectory that, if sustained, puts her at risk of losing again in Iowa.”

Clinton is below the 50 percent mark for the first time, while “Bernie Sanders, riding an updraft of insurgent passion in Iowa, has closed to within 7 points of Hillary Clinton.”

“‘This feels like 2008 all over again,’ said J. Ann Selzer, pollster for the Iowa Poll.”

Only 8 percent of likely caucus goers have a negative view of Sanders, while 19 percent have a negative view of Clinton.

Steve McMahon, an experienced Democratic strategist, said: “These numbers would suggest that she can be beaten. But it’s still early, and Hillary Clinton’s done this before. She knows what it takes to win.”

Perhaps. But if she does lose Iowa, so what? She still has New Hampshire coming up next.

Where the latest poll shows Sanders beating her by 7 percentage points.

Could Hillary lose the first two contests for the Democratic nomination? Unthinkable.

Which means her campaign should be thinking about it every hour of every day.