New York Times reporter Mark Leibovich specializes in spunky profiles of politicians -- hostile profiles of conservatives, flattering ones of liberals.

His latest, on controversial Republican Sen. Jim Bunning, "Republicans Looking for a Reliever in Kentucky," fell safely into the former category, crammed with personal attacks ("questions about his mental fitness") and colorful insults (Bunning's "a bit of a screwball"). The headline is a reference to Bunning's former fame as a baseball pitcher.

Leibovich's latest is similar in tone to his profile of another conservative Republican, former Rep. James Sensenbrenner ("commonly described as 'prickly,' 'cantankerous' and 'unpleasant'"). By contrast, Leibovich has been quite kind to liberals like Al Gore (a "compelling" "pop-culture icon") and Sen. Chris Dodd (a "happy warrior" in a "joyous orbit").

Here's what Leibovich says about Bunning, who's in a fight with his own party and faces a tough re-election in 2010:

Key Republicans are gently (or not gently enough) trying to dissuade Mr. Bunning from seeking re-election in 2010 out of concern that his paltry fund-raising, declining approval ratings and irascible conduct have made him something between vulnerable and unelectable.

But in recent weeks, Mr. Bunning has shown no sign of stepping aside and delivered a string of incendiary pronouncements that have fed an impression that he is, to go with a baseball metaphor, a bit of a screwball.

He declared in a speech last month that the cancer-stricken Justice Ruth Bader Ginsburg would probably be dead in nine months. (He then apologized in a statement that twice misspelled her name.) He threatened to sue the National Republican Senatorial Committee if it backed a primary challenger. And he hinted at a Capitol Hill fund-raiser last week that he was so mad at some in his party that he might just quit and let Kentucky's Democratic governor pick his successor.

Why go after Bunning so harshly? It's not like the House and Senate are free of cantankerous Democrats who make inflammatory comments. Rep. Pete Stark and senior Democrat and former Klansman Sen. Robert Byrd of West Virginia would seem to be prime, pompous targets for a Leibovich cutdown. But he hasn't profiled them.

This next paragraph provided a possible clue: Bunning, you see, is a conservative.

Elected to the Senate in 1998 after six terms in the House, Mr. Bunning, 77, is one of the Senate's most fiscally conservative members. His focus on economic issues -- he sits on the Senate Banking, Budget and Finance Committees -- would seemingly make him a high-profile voice on some of pressing issues of the day. But much of the attention he draws is over his demeanor, not his positions.

Mr. Bunning is known on Capitol Hill for gruffly blowing past reporters and colleagues in hallways and for cranky outbursts at his staff. "He is perceived as being out-of-touch, hot-headed and generally counterproductive," said Phil Musser, a Republican consultant and former official in the Bush administration.

As a native Kentuckian and sports legend in a solidly Republican state, Mr. Bunning long enjoyed a solid base of support. But his penchant for self-immolation nearly cost him re-election in 2004 -- and set off a swirl of questions about his mental fitness....In 2006, Time magazine named him one of the five worst senators in the country.

Well, if an objective source like Time magazine says it, it must be accurate.

—Clay Waters is the director of Times Watch, an MRC project tracking the New York Times.