Hillary Rodham Clinton continues to catch heat for her extensive use of a private email account to conduct official business while she was secretary of state. But the Democrats' 2016 presidential favorite isn't the only White House hopeful whose transparency has come into question.

Several current and former governors who are considering a presidential run have found ways to delay or prevent public scrutiny of their communications while in office. That includes Republicans who have criticized their potential Democratic rival.

"Hillary Clinton's potential evasion of laws is something she should answer questions about," said Kirsten Kukowski, spokeswoman for Wisconsin Gov. Scott Walker, who once used a private email system as executive of Milwaukee County.

Former Florida Gov. Jeb Bush and former Texas Gov. Rick Perry, both Republicans, also criticized Clinton, even though they each used private emails when they held the post as their state's top executive.

A "patchwork" of federal and state public information laws was written "for the era of paper records" that now "aren't serving us well" in the digital age, said Charles Davis, journalism and communications dean at the University of Georgia and an expert on public information laws.

"This is the bedeviling thing: It's good-government law that rests on the honesty and transparency of public officials," he said. "If a government official sets out on a mission to lie to the public or withhold from the public by using private email or some other means, there's not much we can do about it."

Potential White House aspirants now in Congress — including Kentucky Sen. Rand Paul, Florida Sen. Marco Rubio and Vermont Sen. Bernie Sanders — play by a different set of rules than governors. The federal Freedom of Information Act applies only to executive agencies. A request to an agency subject to the act could turn up a letter from a member of Congress, but those members do not have to turn over the documents themselves. Nor do they have to make public any other correspondence, office visitor logs or telephone call sheets that might open a window about who wields influence in their office.

Here's a closer look at how some of the potential 2016 candidates have handled access issues:

JEB BUSH

The former Florida governor, a Republican, made a splash recently by releasing thousands of emails from his two terms, a move that was required under Florida law. Bush also used a private email account, although not exclusively, and he acknowledged that while in office. Like the former first lady, Bush owned the server. And, just as with Clinton, there are questions over the methods he and his associates used to decide which emails to disclose.

CHRIS CHRISTIE

New Jersey law exempts from disclosure agency records that are considered "advisory, consultative or deliberative material," an exception that exists in some form for most governors.

Christie, the current Republican governor, follows an executive order, issued by a Democratic predecessor, that emphasizes the privilege for the chief executive: "All portions of records, including electronic communications, that contain advisory, consultative or deliberative information or other records (are) protected by a recognized privilege."

The Christie administration has applied that exception widely, prompting several ongoing lawsuits. An example: The administration cited security concerns as a reason to deny requests for expense records for his travel outside New Jersey.

Ed Barocas, legal director of the ACLU of New Jersey, said the broader exemptions are important to allow government workers to give advice but also said it is used as a way to shield information from the public. Barocas said courts have held that government emails purely involving facts should be made public.

BOBBY JINDAL

The Republican governor, who campaigned on a platform of providing more transparency in government, uses a private email account to communicate with immediate staff. Those conversations are exempt from public disclosure under a sweeping public records exemption granted to the governor's office under state law.

In 2012, top Jindal aides and some cabinet agency officials used private emails to craft a public relations strategy for imposing $523 million in Medicaid cuts, but the communications did not turn up in an Associated Press records request. Instead, an administration official revealed them anonymously.

It's not clear whether the documents would have been public, anyway. The Jindal administration has often interpreted the governor's "deliberative process" exception to extend beyond his inner circle to all documents generated by any agency for Jindal's office.

Louisiana also has no archiving requirement at all for the governor, making it an outlier nationally. That means records now sealed under that executive privilege may never become public, even after Jindal leaves office.

MARTIN O'MALLEY

The Democratic former governor of Maryland used private emails and his personal cellphone to conduct state business. But his administration also turned over related documents as part of public records requests, sometimes leading to criticism.

In 2012, an environmental group obtained correspondence between O'Malley and a corporate attorney for a poultry producer subject to state regulations.

"I'm guessing you don't have the personal email of governors of DE or VA (Delaware and Virginia), so let me know when (Secretary of Agriculture) Buddy (Hance) can/should be doing more to help you push stuff," O'Malley wrote to Herb Frerichs, who represented Perdue Farms Inc.

The group Food & Water Watch said the exchanges showed a relationship that was too cozy. O'Malley's staff said the activists misinterpreted the governor's tone as uniformly deferential and noted that O'Malley and Frerichs attended law school together.

RICK PERRY

In 2013, amid the then-Texas governor's feud over leadership at the University of Texas system, a Democratic lawmaker's request of university records turned up emails Perry sent from a previously unknown account identified as "R P." In one exchange, the governor used the account to blast as "charlatans and peacocks" critics of his appointees to the university system's governing board.

The Texas attorney general has determined that emails from private accounts are public if they concern state business.

The Perry administration, meanwhile, scrubbed the state email servers every seven days. Perry's successor, Greg Abbott, took office in January and has since widened that frequency to every 30 days.

SCOTT WALKER

Kukowsi, the spokeswoman for Wisconsin's Republican governor, touted the state's "strong open records laws" and her boss's "very specific policies in place in his office" to ensure compliance.

But Walker previously ran Milwaukee County as chief executive using a private email system, which Walker and aides used to discuss government business, campaign fundraising and politics. Two of the aides were eventually convicted for campaigning on government time as part of an investigation that resulted in disclosure of thousands of emails generated on the initially secret system.

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Walker's gubernatorial aides say no such system exists in his current office.

Associated Press writers Gary Fineout in Tallahassee, Florida; Michael Catalini in Trenton, New Jersey; Melinda Deslatte in Baton Rouge, Louisiana; Brian Witte in Annapolis, Maryland; Paul Weber in Austin, Texas; and Scott Bauer in Madison, Wisconsin, contributed to this report.