Curiouser and curiouser.

With apologies to Lewis Carroll, such is the saga of U.S. Sen. Mary Landrieu and her charter-plane flights.

It started simply enough: On July 31, USA Today published an article about 24 senators spending taxpayer dollars on charter flights. The story was based on the most recent of the twice-yearly Senate reports on the accounts the federal government provides each senator for office expenses — mostly staff salaries and travel. The spending — including for charter flights by senators — is legal, provided it’s for official business.

The $47,000 Landrieu paid for charter flights in the 2013 federal fiscal year, which ended Oct. 1, placed her well short of the top spenders — but the article contrasted her with her Republican seatmate, David Vitter, who spent nothing on charters. The USA Today report was seized on by Republicans, who have made Landrieu — a Democrat running for re-election in a red state — a prime target of their drive to win a Senate majority in the fall elections.

“Taxpayers foot Landrieu’s private jet bill,” read one Republican announcement.

Somewhat lost in the hubbub was the information that the spending was not “extra,” in the sense that absent the flights, the money would be available for weapons purchases or border fencing, but rather that it came from the annual appropriation for office expenses. That amount varies, depending on the size of the senator’s state and its distance from Washington, and each senator has considerable discretion in deciding how to spend it.

So had Landrieu not spent the $47,000 on charter flights, she may well have directed it to other office expenses — which, in effect, is the approach Vitter took, and then some. He and Landrieu each were allocated $3 million for the 2013 fiscal year. Landrieu ended the year with $88,000 left unspent, which will go back to the U.S. Treasury. Vitter’s year-end balance was $40,000.

But the news soon turned much worse for Landrieu.

First, CNN reported that Landrieu had billed her office account for a campaign flight from New Orleans to a Lake Charles fundraiser in November — a clear violation of federal laws governing appropriations. Landrieu admitted the error, blamed it on the charter operator and agreed to reimburse the Treasury from her campaign funds.

A second, similar revelation came soon after, and Landrieu again agreed to a reimbursement. She also announced that she had ordered an in-house review of her flight records all the way back to 1997, when she was first elected to the Senate, and said the results would be released publicly by Sept. 8. When additional articles questioning two other flights trickled out, she deferred comment pending completion of the report.

Sept. 8 came — and went, with no report. Republicans sought to make hay from that, and on Sept. 12, the Louisiana Republican Party beat Landrieu to the punch by releasing a list of nine more flights from 2000 to 2008 that they thought looked suspicious, costing nearly $15,000 total.

Landrieu finally released her report later that day, and it went the Republicans several steps better. She flagged 33 campaign-related flights that she said generated improper charges to her office account, and she upped her repayment to nearly $34,000.

But she didn’t go back to 1997: She stopped at February 2002. Nor did she list any flights since March, the last month included in the official reports from the Senate.

Neither omission escaped the notice of the Republicans. Landrieu has said nothing about the flights since Sept. 12, when she blamed “sloppy bookkeeping” for the 33 mistaken billings over a 12-year period. In response to questions, her staff has pointed to the letter from the lawyer who conducted the review, Mark Erik Elias, that was released with the report. Elias has not responded to requests for comment.

Elias’ letter says the review went back no further than Feb. 6, 2002, because that was the day that “the Federal Election Commission announced that mixed-purpose travel may be paid for using a mix of campaign and allocated funds.” That explanation, opaque as it may be, is further clouded by the commission’s statement then that expenses paid from federal government allocations, which presumably would include the Senate office accounts, aren’t subject to its rules.

In any event, Landrieu’s moves to make good on the “sloppy bookkeeping” may mean she avoids any punishment, from the courts or the Senate. The political damage is harder to assess.

Gregory Roberts is chief of The Advocate Washington bureau. His email address is groberts@theadvocate.com and follow him on Twitter, @GregRobertsDC.