VITTER HAS ONE OF THOSE WEEKS…. It was a week Sen. David Vitter (R), the scandal-plagued Louisianan seeking re-election this year, would likely prefer to forget. Unfortunately, for the right-wing senator, it ended on an especially unpleasant note.

On Wednesday, Vitter briefly stopped hiding from the press, fielding a couple of questions in a two-minute media availability. It didn’t go well — journalists pressed the senator on why he kept a violent criminal on the public payroll, and put the man who assaulted his ex-girlfriend in charge of women’s issues.

On Thursday, evidence emerged that Vitter lied to reporters about the aide the day before.

And late yesterday afternoon, the news for Vitter got a little worse.

Scandal-scarred Sen. David Vitter (R-La.) will have a primary challenger after all.

Retired Judge Chet Traylor, who served on the Louisiana Supreme Court for more than a decade, filed his candidacy for the Republican nomination in the last few minutes before the filing deadline Friday evening.

Vitter has endured a series of controversies in his first term in office, and public polls from last year showed him in a weak position against a potential challenger in the Aug. 28 primary, though he continues to hold a solid lead over the likely Democratic nominee, Rep. Charlie Melancon (D-La.).

News of a primary fight isn’t exactly new. Indeed, after Vitter was caught committing adultery with prostitutes after having run on a “family values” platform, it was largely assumed that the humiliated senator would struggle.

A variety of Louisiana Republicans, including Suzanne Haik Terrell, Tony Perkins, and Secretary of State Jay Dardenne, publicly flirted with a primary challenge, but backed off. Traylor, however, quietly worked to assemble a team — he has an extensive list of friends within the state GOP establishment, especially deep-pocketed conservative business leaders — and submitted his paperwork with literally just minutes to go before the filing deadline.

Vitter’s incumbency and financial advantage positions him as the favorite in the primary, but the contest will force him to spend time and money he hoped to devote to the general election, and will create fissures among in-state Republicans. Indeed, David Kurtz suggests Traylor’s candidacy might be evidence that “the business community is abandoning Vitter.”

A primary race that didn’t exist 24 hours ago has instantly become one of the season’s most interesting contests. Something to keep an eye on.

Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.