Most presidents encounter an event that solidifies the public's view of their competence, for good or bad. Some events are so big that once the public makes up its mind that a president and his team are in over their heads, it becomes impossible to restore confidence.

This was the situation that President George W. Bush found himself in when Hurricane Katrina devastated New Orleans and the Gulf Coast in 2008, leaving nearly 2000 persons dead and some 400,000 displaced from their homes.  The Pew Research Center for the Public and the Press found that "What might have damaged Bush's legacy most was his administration's mixed record of competent governance. Between Iraq, the government's flawed relief effort in the aftermath of Hurricane Katrina, and more minor missteps over the Dubai ports issue and other matters, the government 'brand' deteriorated badly during the Bush years. In late April 2008, just 37% expressed a favorable view of the federal government, about half of the percentage of five years earlier (73%)."

Some pundits and reporters today argue that the technological problems plaguing the rollout of the Obamacare web portal is President Obama's Katrina moment.

National Journal columnist Ron Fournier on Tuesday's Morning Joe with Joe Scarborough: "Just like Katrina, when the big problem President Bush had was diminishing the significance of what was happening, saying 'Hey, way to go, Brownie,'—you had the president yesterday talking about glitches and kinks. This is bigger than glitches and kinks."

Former George W. Bush Communications Director Nicolle Wallace: ""The one difference was Katrina was a storm, the health care law was Obama's creation. I'm not defending my White House's handling of Katrina, but it was a natural disaster. This was a disaster of Obama's creation and imagination."

Is  it fair to compare the Katrina with the Obamacare rollout?

Let's start with the obvious.  The Obama administration blew it, big time, in launching the enrollment hub on October 1 when it knew it wasn't ready for prime time.  The  president and his team were too late to get on top of it.  The administration's ineffective managing of the rollout is eroding public confidence in Obamacare.  "The public's impression is that it has been a bumpy launch," says the Pew Research Center, with only "29% saying that the online health insurance exchanges are working very or fairly well."  With public trust in the federal government after the shutdown also at a near historic low, poor rollout of the Obamacare exchanges could eventually convince the public that the government is incapable of taking on responsibility for managing much of the health care system.

But it is wrong and offensive to suggest that the messy exchange rollout is Obama's Katrina.   The troubled Obamacare rollout has temporarily prevented people from getting health insurance, but there is still time to get the problems fixed. By the time the government woke up to  what was happening with Katrina, people had already died.

There is another big difference.  After Katrina, the oversight investigations into the government's failed response were with the purpose of ensuring that next time, the government would be ready to help before it is too late.  No one was questioning whether the federal government had a responsibility to help those in need because of a natural disaster, no ideology that said that if a deadly storm comes, you are on your own, tough luck, don't look to the government for assistance.  And because of the lessons learned from Katrina, the government did much better when Hurricane Sandy hit New Jersey and New York last year.

But many of the people today who are investigating the Obamacare rollout don't really want to learn how to make it work better.  Instead, they want to discredit the very idea that the federal government has a role in helping people get coverage, driven by an ideology that says if you are sick and uninsured, tough luck, don't look to the government for help.

The difference, then, is between a botched government response that temporarily is making it harder for some uninsured people to get health insurance, and a botched government response to a storm that killed and displaced thousands because of its negligence.   There is no comparison.