The shape of the 2010 battleground remains largely in flux 17 months away from Election Day, but House Democrats continued to reap the benefits of their majority status by posting strong second-quarter fundraising numbers this week.

In 40 targeted districts featuring incumbents, newly-filed fundraising reports showed that 10 of 30 Democrats had raised $300,000 or more, and three more incumbents falling just short of that mark.

Standing out among the group was Rep. Jim Himes (Conn.), who raised more than $500,000 in the second quarter and currently does not have a Republican opponent. Fellow Democratic Reps. Chet Edwards (Texas) and Gary Peters (Mich.) each raised more than $400,000.

Of the fundraising reports Roll Call surveyed of vulnerable Democrats, a dozen posted more than $500,000 in cash on hand; Peters, Edwards and Rep. Zack Space (Ohio) all have more than $800,000 on hand.

Meanwhile, four of the 10 Republicans on the list of 40 battleground races broke the $300,000 barrier, while Rep. Michele Bachmann (R-Minn.) came close to it.

The latest fundraising numbers show that while some of the top 2010 House races are beginning to take shape, it is still relatively early in the cycle and both parties, but especially Republicans, still face the burden of filling key recruiting holes.

There was also good news for House Republicans in the latest round of Federal Election Commission reports.

It appears that the National Republican Congressional Committee’s new “Patriot— program, which was unveiled in February by Chairman Pete Sessions (Texas), is paying off.

The program is geared toward helping targeted incumbents prepare for the 2010 elections and Democratic officials say the program is based on their own successful “Frontline— program.

Ten GOP incumbents were included on the first list of “Patriots— and those Members posted respectable numbers during the second quarter.

Rep. Anh “Joseph— Cao (R-La.), who is considered the most vulnerable House Member, brought in $370,000 after a fairly weak first quarter showing. Rep. Dave Reichert (R-Wash.) wasn’t far behind with $332,000 in receipts while Reps. Leonard Lance (R-N.J.) and Dan Lungren (R-Calif.) both brought in more than $200,000.

But Lungren was one of a handful of Republicans who were outraised by their Democratic challengers this cycle. Physician Amerish Bera (D) raised $288,000 to Lungren’s $238,000.

In addition to Lungren, Rep. Bill Young (R-Fla.) was outraised by $26,000, Rep. Mary Bono Mack (Calif.), was outraised by $27,000 and Rep. Mike Castle (Del.) was outraised by $137,000.

Castle’s second-quarter performance all but confirms that the moderate Republican is not likely to seek re-election and will either retire or run for Senate. Delaware Lt. Gov. John Carney (D), who raised $262,000 in the period, will be heavily favored to win the at-large seat if Castle leaves.

Former Pentagon official Bill Russell (R) raised a stunning $649,000 in the second quarter for his race against Rep. John Murtha (D-Pa.), who raised just $133,000.

Russell was among a handful of Republican challengers to outraise a Democratic incumbent in the quarter, but his campaign’s high burn rate left him lagging in available cash. Russell spent $578,000 and trailed Murtha by about $190,000 in cash on hand as of June 30. Reps. Loretta Sanchez (D-Calif.) and John Hall (D-N.Y.) were also outraised by their Republican challengers in the period. Democrats are currently favored to hold all three of those districts.

After Russell, former Arizona state Rep. David Schweikert (R) and Manchester, N.H. Mayor Frank Guinta (R) came the closest to matching the second quarter haul of the Democratic incumbents they are facing. Schweikert raised $228,000 to Rep. Harry Mitchell’s (D-Ariz.) $250,000. Guinta took in $110,000 to Rep. Carol Shea-Porter’s (D-N.H.) anemic $130,000 showing.

Florida state Sen. Charlie Justice (D) also posted a particularly weak showing during the quarter. Justice did outraised Young — who is viewed as a retirement possibility — in Florida’s 10th district, but most observers expected more than just $80,000 out of the highly-touted Democratic recruit.

Meanwhile, a few Republican recruits also posted unimpressive second quarter numbers. Veteran and former CIA officer Vaughn Ward (R), running against Rep. Walt Minnick (D-Idaho), raised just $75,000 for the quarter. And though Rep. Peter DeFazio’s (D-Ore.) district is not on the top 40 battleground list, his opponent, Springfield Mayor Sid Leiken (R), raised just $33,000.