We learn the most about someone’s character not from what he does when he knows others are watching but from what he does when he thinks they aren’t.

We’ve learned an awful lot of troubling things about Mitt Romney recently. First, his sweeping, closed-door condemnation of President Barack Obama’s supporters revealed the disdain he has for half the population he hopes to serve. Then, the limited tax returns Romney selectively released confirmed that he’s willing to share information about the time he’s been in the public eye and running for president, but not the time he was running the corporation he touts as his sole qualifying credential for the highest office in the land.

When he thought no one was listening, Romney accused 47 percent of Americans of not taking responsibility for their lives, painting them as lounging in government dependency — a conclusion he reached because, for various legitimate reasons, they are exempt from paying federal income taxes.

Romney stands not only on shaky ethical grounds in making that indiscriminate generalization — he’s also on flimsy factual footing. The 47 percent Romney derides as self-pitying “victims” includes seniors who live on a fixed income thanks to the Social Security they paid into and earned over a lifetime of hard work, our troops in combat zones and veterans who have fought for our country. It includes students studying to get the skills that will win them the jobs of the future and decent Americans actively looking for work because their jobs were outsourced by companies such as those Romney specialized in developing. Most of them pay plenty of payroll, property, local and state taxes.

None of these Americans is looking for a handout or shortcut. That Romney waited until he thought all the cameras and microphones were off before insulting the millions he belittled as “those people” unworthy of his concern calls into question his judgment, leadership and fitness for the public trust. If you’re not willing to fight for every American, you don’t deserve to represent any of them.

The second lesson we learned came at another time Romney thought no one was looking: He released his 2011 tax returns late on a Friday afternoon in the hopes of making the smallest news splash possible.

What was he trying to hide? Perhaps that, despite his tough talk on China, he profited from investments in a state-owned Chinese oil company and a video company known for pirating copyrighted content. Or that, despite calling Russia our “No. 1 geopolitical foe” and his fiery rhetoric against Iran, he invested in Russia’s state-owned oil giant, which does business with Iran. Or that the candidate with the slogan “Believe in America” has been betting against the U.S. dollar by buying foreign currencies and keeping his investments in the Caymans and Bermuda. Or maybe he was hoping no one would notice that he paid just 14 percent of his $14 million income, a rate lower than many middle-class families pay.

Romney’s pre-weekend release was one big head fake, hoping that the measly two years of tax returns he has released would distract us from remembering that he still hasn’t released a single one from before his candidacy. It would be far more helpful for voters to see what tax loopholes he was exploiting and which foreign accounts he was favoring over American institutions when he didn’t know he’d ever have to reveal them. And since Romney likes to divide people based on what income tax rate they pay, it would certainly help to know his own — and whether he includes himself in the 47 percent he thinks aren’t pulling their weight.

Here’s what we know: Romney has these records ready — he gave John McCain 23 years’ worth before he lost the vice presidential nomination to Sarah Palin and gave his accountants 20 years so they could release a CliffsNotes version that voters have no way of verifying. We also already know this self-described “severely conservative” man takes some pretty liberal deductions; now we know that includes writing off half of the country.

The offensive comments Romney hoped would stay private and the remaining tax returns that he’s still withholding from the American people are important because they are windows into the character, values and priorities of someone who could drive our nation’s economic policy.

Obama wants to eliminate the special loopholes Romney exploits but that are unavailable to most Americans; Romney, of course, wants to protect them. Romney also plans to raise taxes on the middle class to pay for even more tax cuts for millionaires and billionaires. He may mock redistributive policies, but Romney is proposing the largest redistribution of wealth from the bottom to the top in American history.

Recognizing he’s president of all Americans, Obama has a different plan: Everyone should pay their fair share so we can responsibly reduce the deficit in a balanced way and make investments in areas proven to fuel growth from the middle out, such as education, jobs, innovation and energy. It’s a plan the president believes in and has made public for all to see. He’s the only candidate in this race who believes those should be one and the same.

Sen. Harry Reid, D-Nev., is the majority leader of the U.S. Senate.