Seven of the 10 most frequent users of tax-paid congressional mail are also among those facing the toughest re-election battles.

The privilege known as "franking" allows members of the House and Senate to send publicly funded radio, postal mail and telephone messages.

The messages are supposed to deal only with official business and cannot be sent less than three months before a primary or general election.

Even so, a Washington Examiner analysis of congressional spending accounts found millions of tax dollars being spent on what amounts to free advertising for House members.

The pre-election restriction is meant to keep official business and re-election campaigns separate, but the overlap between members who frank the most and RealClearPolitics' list of the 75 most competitive House races suggests that franking is not so detached from electoral politics.

Rep. Paul Cook, a first-term Republican from California's 8th Congressional District, spent $365,000 on franked mail in his first 15 months in office, more than any other representative. The median franking expenditure by House members was only $33,000.

Cook attributed his spending to the size and remoteness of his desert district, saying, "My district is one of the largest geographically. ... Communication and travel is difficult, so mail is still the best and cheapest way to keep the most people informed.”

Cook is not on RCP's list, but Rep. Mike Coffman, R-Colo., is. Coffman spent $260,000 on franked mail, including $15,000 on non-postal communications, between January 2013 and March 2014. That ranks him ninth in Congress.

Politico ranked Coffman's battle for re-election against Democrat Andrew Romanoff as potentially the nation’s toughest contest.

Critics, including National Taxpayers Union President Pete Sepp, are not surprised by the overlap between frequent franking and shaky electoral prospects.

"Suspicions are being confirmed about franking's ability to help protect endangered incumbents," Sepp said.

Highest-spending frankers
Member Total Non-mail
Paul Cook (R-CA) $365,436 $2,500
Pedro Pierluisi (D-PR) $327,634 $327,634
Julia Brownley (D-CA) $308,196 $0
Dennis Heck (D-WA) $292,437 $47,374
Doug Collins (R-GA) $278,976 $58,205
John Garamendi (D-CA) $277,244 $59,925
Ami Bera (D-CA) $269,572 $84,560
Raul Ruiz (D-CA) $265,292 $0
Mike Coffman (R-CO) $259,870 $15,000
Ann Kirkpatrick (D-AZ) $259,636 $170,152
Covers January 2013-March 2014. Bold names are in tight elections.
Source: Statements of Disbursements

Adding to the impression that franking lets incumbents use tax dollars to boost their election prospects is the fact that senators rarely use the privilege.

From January 2013 to March 2014, House members spent nearly $30 million and senators spent only $614,000. In 2010, the House spent nearly $50 million on franked mailings.

Franked mail has been an issue almost as long as Congress has been in existence.

A 1972 essay in the Loyola of Los Angeles Law Review quoted a senator in the 1960s as saying, “It was not intended that the Congress extend free junk-mailing privileges to political candidates who happen to hold office in the Congress."

The essay argued that franking “allows the incumbent candidate to subsidize his campaign by virtue of his office.”

Franking was partially abolished once. The Senate banned franking in 1873 but restored it in 1894.

The ban came after widely acknowledged abuses that reached their peak when a senator transported his horse from Washington to Pittsburgh by terming the animal an “official document” and signing its bridle, according to the Senate Historical Office.

In addition to the pre-election moratorium on franked mail, members of Congress cannot make partisan attacks in their mailings and there are limits on the number of pictures of themselves and the amount of biographical information they may include.

The restrictions, as well as the declining relevance of postal mail, have had an impact. The Senate slashed its mail costs from $44 million in 1984 to $2.5 million in 2009, according to a Congressional Research Service report, and House spending has declined from nearly $80 million in the 1980s.

Other measures to reduce franked mail have failed to gain traction. When Sen. Jeff Flake, R-Ariz., was a member of the House, he introduced legislation requiring franked mail to go out on official letterhead rather than with eye-catching graphics. Another bill would have required the mailings to include their total cost, while a third would have eliminated them entirely.

NTU's Sepp said the fact that a complex maze of rules is needed to regulate franked mail means the whole concept should probably be jettisoned.

"All of this is a tacit admission that the franking privilege, however carefully regulated, can create a subtle advantage for incumbents over challengers,” Sepp said.

Another factor in the debate about the future of franking was the emergence in 2009 of a new category called franked “communications.”

That category includes robocalls, tweets and Facebook ads, and even radio and television ads.

Rep. Ann Kirkpatrick, D-Ariz., who ranked 10th in spending on franking, spent $17,000 in taxpayer funds to air ads on a radio station. Rep. Richard Nugent, R-Fla., also used the franking privilege to buy radio ads.

In the first quarter of this year, the most recent for which data is available, Rep. Ami Bera, D-Calif., sent 161,000 mailings at a cost of $78,000. Bera also made 2.5 million impressions through non-postal means that cost only $24,000.

Bera's spokesman, Allison Teixeira, said the first-term congressman “has fought against spending taxpayer money on raises and perks for members of Congress, and has given his own congressional pension back to the U.S. Treasury.”

Both men are on RCP's list of endangered members of Congress.

Rep. John Garamendi, D-Calif., had the sixth-highest expenditures this Congress — and has regularly bought Facebook, radio, newspaper and even $7,000 of TV ads — which he attributed to the geographic nature of his district.

"I represent a large, rural district, and mail, phone, radio, email, and social media communications are the best ways to keep my constituents informed about my office's work," Garamendi said.

CORRECTION: Rep. John Garamendi's $7,000 television ad buy, funded by tax dollars, was made in 2012 and was not part of the $277,244 in franking referenced in a table that appeared with this story. The Washington Examiner regrets the error.