Give Barack Obama credit. He never claimed he had the executive experience many Americans feel is essential for a president.

Go back to October 2006. There was much buzz that Sen. Obama, newly arrived in Washington, would run for the White House. "You've been a United States senator less than two years, you don't have any executive experience. Are you ready to be president?" the late Tim Russert asked Obama on NBC.

"Well, I'm not sure anybody is ready to be president before they're president," Obama responded. "You know, ultimately, I trust the judgment of the American people."

That didn't exactly answer the question. Obama's theory was that if he could survive the rigors of a campaign, and voters chose him to be president, then he was ready to be president. He didn't say anything about actually running the executive branch of the U.S. government.

A couple of months later, in December 2007, Obama again appeared on NBC and was again asked why Americans should vote for a candidate with no executive experience.

"People desperately want change," he answered, explaining that he could "bring people together to get things done" and "make sure that the voices of the American people aren't drowned out." Again, there was nothing about actually running the government.

When it came to the question of executive experience, Obama was lucky in the 2007-2008 Democratic primary season. Most of his rivals didn't have any such experience, either. Hillary Clinton, John Edwards, Joe Biden, Chris Dodd, and others -- none had even a bit of executive experience, although some Clinton supporters tried to argue that her years as first lady should count.

New Mexico Gov. Bill Richardson was the only real contender in the Democratic race who had actually run something. "I think prior executive experience is very important," Richardson said at a January 2008 debate in New Hampshire. "I'm the only governor here. I'm the only person here who has actually balanced budgets. ... You want somebody in this position that has had executive experience."

Voters didn't buy Richardson's argument. And Obama was lucky again in the general election, as far as executive experience was concerned, when Republicans chose a senator without any such background as their nominee. (Some John McCain supporters tried to argue that his time in the military counted as executive experience.) The '08 election was the first in nearly a half-century in which executive experience, usually in the person of a former governor or vice president, was not on the ballot.

In 2012, Mitt Romney, a one-term governor of Massachusetts, tried to make executive experience an issue. But of course by that time Obama had been president four years. The experience issue was a non-issue.

That's not true any more. Last fall's disastrous rollout of Obamacare did terrible damage to the public's trust in Obama's ability to run the government. A November 2013 CNN poll found that just 40 percent of those surveyed believe Obama "can manage the government effectively."

Fixing the Obamacare website -- sort of -- did little to improve Obama's reputation. In a Quinnipiac poll in January of this year, 53 percent said the administration is not "competent in running the government," while just 42 percent said it is competent.

Now comes the Veterans Affairs hospital scandal, and the president again appears in over his head. It seems inevitable that public opinion of Obama's competence will fall still more. The president and Democrats can blame Republicans -- has there ever been a moment when they didn't? -- but the fact is, voters have less and less faith in Obama's ability to run the government.

That loss of faith could shape his last two years in the White House. Obama has two great policy goals left -- to "fix" the nation's "broken" immigration system, and to enact draconian restrictions on carbon emissions.

At the moment, Congress won't do either one. There are lots of reasons Republicans oppose Obama's initiatives. But the issue of executive competence alone would be reason enough to oppose; why should GOP lawmakers entrust far-reaching new authority to a president who is struggling to run the executive branch as it is?

In a February 2008 candidate forum, Obama conceded that "most of my career has been in a legislative role." But he pointed to his campaign as evidence of his executive abilities, noting that it was "a $100 million-plus operation with hundreds of employees around the country."

One hundred million dollars! How about that! Of course, the federal government spends more than four times that much every hour, for a total approaching $4 trillion a year.

Running the federal bureaucracy is a considerably bigger job than running a campaign. Maybe next time, voters will take that into account.