A PILLAR of American democracy is the tenet that no one is above the law, not even the president of the United States, as was amply illustrated by the Watergate scandals that brought down Richard M. Nixon. This is why the integrity of presidential candidates draws justifiable attention during the race. A president must have the right stuff — the right judgment and temperament — not only to respond to crises and wars but also to preserve and lead a system based on laws.

Thus it is very disturbing to see evidence that four undeclared candidates for the presidency, from both parties, have made questionable judgments about campaign finance laws. According to complaints filed by two activist groups that favor more openness, the Campaign Legal Center and Democracy 21, the four are sidestepping restrictions on fundraising and spending activity on those who are “testing the waters” before deciding whether to run.

The Federal Election Commission has established rules for those in this phase, but the four are simply skirting the rules by saying they are not really testing the waters. Those named in the complaints are former Florida governor Jeb Bush (R), former Maryland governor Martin O’Malley (D), former senator Rick Santorum (R-Pa.) and Wisconsin Gov. Scott Walker (R).

All deny doing anything wrong: Mr. Bush’s spokeswoman told us, “We are acting appropriately and within the law.” But this behavior seems too clever by half. The candidates are out campaigning, raising money, hiring staff, giving speeches — and saying that they are not testing the waters. Aside from the legal issues, it is troubling to see would-be presidents playing fast and loose with the rules. The candidates may be gambling that the gridlocked FEC will never be able to surmount partisanship and launch an enforcement action, but that hardly reflects the kind of integrity one would desire in a president.

In this era of “dark money” in American politics, Mr. Bush has taken another step that causes deep concern. As The Post’s Ed O’Keefe and Matea Gold reported Wednesday, a friend and former staffer has set up a nonprofit “social welfare” organization, tax-exempt under the Internal Revenue Code, that will reportedly develop policy options that are “consistent” with those held by Mr. Bush. The group is called Right to Rise Policy Solutions, and under existing rules it will not have to disclose the identity of its donors nor will contributions be limited. The Internal Revenue Service has been reviewing the use of these groups, known as 501(c)(4)s, in politics for some time. But Mr. Bush seems to have no compunction about making use of one. He and his allies have created two other political action committees, also called Right to Rise, one of which is a supposedly independent super PAC with donors disclosed but no limits on contributions.

Mr. Bush seems to have adopted every dark-money trick in the book. Will others now follow? As it is, the presidential campaign will begin under a dark-money cloud. Americans want a president with the right stuff, and that does not mean bags of secret cash.