WASHINGTON -- The Campaign Legal Center has filed complaints against four likely presidential candidates for violating federal law by using outside groups to serve as shell campaigns before they officially declare a run. The complaints filed with the Federal Election Commission identify Republicans Jeb Bush, Rick Santorum and Scott Walker and Democrat Martin O’Malley as acting like candidates while not following federal finance regulations.

“These 2016 presidential contenders must take the American people for fools — flying repeatedly to Iowa and New Hampshire to meet with party leaders and voters, hiring campaign staff and raising millions of dollars from deep-pocketed mega donors, all the while denying that they are even ‘testing the waters’ of a presidential campaign,” said Paul S. Ryan, senior counsel for the Campaign Legal Center. “But federal campaign finance law is no joke and the candidate contribution limits kick in as soon as a person begins raising and spending money to determine whether they’re going to run for office. Bush, O’Malley, Santorum and Walker appear to be violating federal law.”

In campaigns past, candidates followed a common process. If someone was interested in running for president, they formed an exploratory committee that was used to raise money and pay for expenses like traveling to early primary states. But with the advent of the super PAC, that process has almost entirely died. Only two candidates have opted this year to form an exploratory committee -- former Virginia Sen. Jim Webb, a Democrat, and Ben Carson, a Republican. Sitting members of Congress, like Republicans Rand Paul and Marco Rubio, have some wiggle room to use their Senate campaign funds.

Wisconsin Gov. Walker created a “527 political committee,” named for a part of the tax code that allows groups to raise money to influence campaigns, called “Our American Revival.” Former Florida Gov. Bush, in announcing that he was considering running for president, launched the “Right to Rise PAC” and is aiming to raise $50 million through the group. Former Sen. Santorum of Pennsylvania launched his “Patriot Voices” PAC after he wrapped up his failed 2012 campaign. And former Maryland Gov. O’Malley has been using his PAC, “O’ Say Can You See,” since 2012 to support other Democrats and raise funds as his national profile increased.

All four men have been making public appearances and raising money through their PACs or similar committees, which aren’t subject to campaign finance limits. The PACs can raise and spend without limits. And all four have been hiring staffs that would presumably work for a presidential campaign but in the meantime are employed by the PACs.

O’Malley’s spokeswoman Lis Smith refuted the complaint. “Our PAC has been fully compliant with the law," she said. "This complaint has no merit and we are confident that -- whatever the case may be with the other potential candidates -- that is what the FEC will find."

Bush’s office insisted that they were not in violation. "We are fully complying with the law in all activities Gov. Bush is engaging in on the political front,” spokeswoman Allie Brandenburger said. “If Gov. Bush engages in any testing-the-waters activities, they will be paid for appropriately under the law and reported at the required time."

Neither Santorum's office nor Walker’s responded to request for comments.

UPDATED 8:30 p.m.: Walker's organization dismissed the complaint as well. "Gov. Walker has been talking to Americans about his reform-minded principles in Wisconsin through the issues based organization Our American Revival," spokeswoman Kirsten Kukowski said. "If there are any announcements about his future he will do it in accordance with the law."