Rep. Anh “Joseph— Cao (R-La.), who is viewed by most race watchers as the most vulnerable incumbent of the 2010 cycle, had a second straight strong fundraising quarter, bringing in nearly $400,000 from July through September.

But Cao’s fundraising success is tempered by a high burn rate during the third quarter. Cao raised $394,000 in the period but spent $382,000, leaving him with just $351,000 in cash on hand as of the end of September. That’s just $11,000 more in the bank than Cao had at the end of June.

Most of Cao’s expenses during the quarter came from the high cost, high reward of direct-mail fundraising. Cao spent more than $250,000 on direct-mail costs during the three-month period.

Cao’s fundraising has been a bit of a roller coaster ride this year.

After raising less than $150,000 during the first three months of the year and reporting an unimpressive $61,000 in the bank on March 31, Cao reported $370,000 in receipts in the second quarter and almost $340,000 in cash on hand as of June 30.

And while his first-quarter report included donations from just a handful of fellow Republican lawmakers, Cao’s second-quarter report was boosted by checks from more than 15 Republican Members including many Republican leaders.

During the third quarter, Cao received checks from GOP Reps. John Mica (Fla.), Shelley Moore Capito (W.Va.), John Kline (Minn.), Glenn Thompson (Pa.) and Lynn Westmoreland (Ga.).

State Rep. Cedric Richmond (D), who filed in mid-August to run against Cao, said earlier this month that he will report raising more than $100,000 in his third-quarter Federal Election Commission report.

State Rep. Juan LaFonta (D) has also filed for the race.