With campaign cash flowing quickly into several open-seat House elections, the contours of many of these races already are beginning to take shape.

The most recent fundraising reports for these races, which cover the period from July 1 to Sept. 30, may not reveal much about whether the Democrats are in a position to make significant gains overall in next year’s fight for control of the House. But they at least offer clues as to how some of the battlegrounds will look. Among the highlights:

• In Florida’s 13th district, which Rep. Katherine Harris (R) is abandoning to run for Senate next year, two Republican businessmen already have banked hundreds of thousands of dollars, and the leading Democrat also made a respectable showing in the most recent fundraising period.

• In Iowa’s wide-open 1st district race, both primaries have seen financial frontrunners solidifying their positions, though their victories are by no means assured.

• In Colorado’s 7th district, two well-stocked Democrats appear destined to slug it out, while one strong Republican remains above the fray.

• Three strong and cash-flush Republicans are battling hard in Minnesota’s 6th district, and the same is true in Nevada’s 2nd district. But Democrats are hopeful in both districts, despite their Republican lean.

• The identities of frontrunners are now clear in Florida’s 11th district and in Illinois’ 6th district.

• A well-funded newcomer could transform the Republican race to succeed Rep. Duke Cunningham (R) in California’s 50th district.

• Finally, what promises to be a knock-down, drag-out general election fight in Ohio’s 6th district appears to be well under way.

Of all of these seats, money has been flowing fastest into the race to succeed Harris in the Sarasota-based 13th district. Auto dealer Vern Buchanan (R) raised an impressive $588,000 during the three-month period, finishing with $472,000 in the bank. His chief GOP opponent, banker Tramm Hudson, collected $196,000 and banked $310,000.

Both Buchanan’s and Hudson’s totals dwarf the intake of a third Republican, state Rep. Nancy Detert, who raised just $46,000 and had $39,000 left in the bank.

Although the district gave President Bush 56 percent of the vote in 2004, Democrats have some hope of competing there. Their leading candidate, bank president Christine Jennings, raised $136,000 for the three-month period and had $205,000 on hand as of Sept. 30.

Meanwhile, the Republican race to succeed Rep. Jim Gibbons (R) in Nevada’s 2nd district is turning into a costly three-way battle. Fueled by an endorsement from the conservative Club For Growth, state Assemblywoman Sharron Angle (R) led the pack, collecting $100,000 in the third quarter and finishing with $259,000 in the bank.

But Angle trailed the favorite of the GOP establishment, Nevada Secretary of State Dean Heller, in cash on hand. Heller banked $299,000 through Sept. 30.

Former state Assemblywoman Dawn Gibbons (R), who is seeking to succeed her husband in Congress as he runs for governor, is also proving her mettle as a fundraiser, taking in $99,000 and banking $207,000.

Despite the politics of the sprawling district — Bush took 57 percent of the vote there — Democrats hope that the GOP primary becomes a bruising affair, paving the way for their likely nominee, former state Regent Jill Derby. In her first few weeks as a candidate, Derby raised $109,000 and banked almost all of it.

The same scenario is in play in Minnesota’s 6th district, where Rep. Mark Kennedy (R) is leaving to run for the Senate. Three Republicans are running hard for the nomination. So far, the financial leader is another Club for Growth-backed candidate: state Rep. Phil Krinkie (R), who had $225,000 in the bank on Sept. 30.

But Democrats are high on their likely nominee, the moderate-to-conservative former state Transportation commissioner, Elwyn Tinklenberg, who was sitting on $111,000 at the end of the quarter.

The opposite dynamic may exist in Colorado’s swing 7th district, where Rep. Bob Beauprez (R) is running for governor. This represents one of the Democrats’ best pick-up opportunities, but two top-tier candidates are running against each other in the primary: former state Sen. Ed Perlmutter, who raised $105,000 in the quarter and had $259,000 left in the bank, and ex-state Rep. Peggy Lamm, who raised $89,000 and had $121,000 on hand.

As Lamm and Perlmutter battle it out, the likely GOP nominee, Rick O’Donnell, continues to raise money aggressively, and had $365,000 in the bank on Sept. 30.

Another tossup race is taking shape in Ohio’s 6th district, where Rep. Ted Strickland (D) is leaving to run for governor. There, state House Speaker Pro Tem Chuck Blasdel (R) raised $237,000 in the past three months and banked $218,000. State Senate President Charlie Wilson (D) took in $166,000 and had $212,000 left over.

On the other hand, a few other open-seat races now seem less competitive than they once did. In Florida’s 11th district, where Rep. Jim Davis (D) is leaving to run for governor, Hillsborough County Commissioner Kathy Castor (D) has a substantial fundraising lead over her three Democratic primary opponents and must be considered the frontrunner at this stage.

And in Illinois’ 6th district, where Rep. Henry Hyde (R) is retiring, state Sen. Peter Roskam (R) appears to have a commanding lead in every respect. He already has cleared the Republican field and has a big financial advantage over the Democratic contender, 2004 nominee Christine Cegelis.

Roskam raised $286,000 from July 1 to Sept. 30 and reported $550,000 on hand. Cegelis, by contrast, took in just $52,000 and had $49,000 in the bank.

Because Democratic Congressional Campaign Committee Chairman Rahm Emanuel (Ill.) represents an adjoining district, national Democrats maintain some hope that they’ll be able to recruit a stronger candidate into the race. But they have to hurry: Illinois has the earliest filing deadline of the 2006 cycle, Dec. 19, 2005.