The 2010 Senate battleground is far from developed as early retirement announcements and presidential appointments have further muddied the landscape.

But year-end fundraising reports filed over the weekend offered some early insight into the strengths and weaknesses of both parties.

While it’s clear that the competitive terrain remains very fluid and that recruiting efforts will be key to both sides’ success in 22 short months, Democrats can claim a few early victories.

Chief among them is the fact that the Democratic incumbent who is considered most vulnerable in 2010 — Senate Majority Leader Harry Reid (Nev.) — appears to be in a better financial position than several GOP incumbents who are being targeted this cycle.

Sensing a weakness back home, the National Republican Senatorial Committee has already targeted Reid with television ads in his state and made clear it plans to attack the Democratic leader early and often. But Reid was sitting on $3.3 million as of Dec. 31, with more than $800,000 raised in the last three months of the year. The Republican most often mentioned as a challenger, former Rep. Jon Porter, had just $26,000 in cash on hand after losing his re-election bid to now-Rep. Dina Titus (D).

Sen. Jim Bunning (R-Ky.), who is considered his party’s most endangered incumbent, reported a paltry $150,000 in cash on hand and just $28,000 raised in the fourth quarter of 2008. Bunning barely survived his 2004 re-election bid against now-Kentucky Lt. Gov. Dan Mongiardo (D). Mongiardo plans to run again in 2010, and Bunning continues to be the subject of a whisper campaign among Republicans who feel their chances of holding the seat are stronger with him gone. Bunning’s fundraising numbers aren’t helping quiet those whispers.

In North Carolina, Democrats are also keen on challenging Sen. Richard Burr (R) after his Tar Heel State colleague, Sen. Elizabeth Dole (R), went down in defeat in 2008. Burr ended the year with just over $1 million in the bank after raising just $89,000 in the last quarter of the year. Rep. Heath Shuler, who some Democrats hope will challenge Burr, ended the year with $944,000 in the bank after raising $184,000 from October through December.

Among the several Republicans being targeted early by Democrats, only Sen. Arlen Specter (Pa.) can claim a fundraising lead similar to Reid’s.

Specter, who is also running in a state where Democrats have made recent inroads, reported $5.8 million in the bank at the end of 2008 and $611,000 raised in the fourth quarter.

Of the two Democratic House Members being mentioned as possible Senate contenders in Pennsylvania, Rep. Allyson Schwartz was sitting in the better financial position. She reported just under $2 million in the bank at the end of 2008 compared with just $147,000 for sophomore Rep. Patrick Murphy.

With a few reports still outstanding, Sen. Evan Bayh (D-Ind.) was among those in the running to report the most cash on hand as of Dec. 31. He reported more than $10.8 million in the bank, which can be attributed in large part to an aborted White House bid last cycle.

Federal Election Commission reports were not available Monday for Sen. Richard Shelby (R-Ala.), who consistently reports having a healthy multimillion-dollar campaign war chest despite the fact that he never faces competitive challenges.

In 2010, Republicans will be defending 19 seats and Democrats 17 — although there also remains the chance that Sen. Kay Bailey Hutchison (R-Texas) could leave her seat early in advance of a gubernatorial bid.

The cycle has already been notable for a slew of early retirement announcements by GOP Sens. Mel Martinez (Fla.), Sam Brownback (Kan.), Kit Bond (Mo.) and George Voinovich (Ohio).

For the most part, the primary fields in those contests are continuing to develop. For Democrats, their chances of making the races competitive rest largely with their ability to coax top-tier challengers to run in the coming months — potential candidates such as Kansas Gov. Kathleen Sebelius (D) and Missouri Secretary of State Robin Carnahan (D).

One of the few places where at least one party’s field appears to be settling is in Ohio, where national Republicans are set to rally behind former Rep. Rob Portman. As of Dec. 31, Portman reported a healthy $1.5 million in the bank. Democrats are continuing to sort out who their desired candidate is. Among those mentioned is Rep. Tim Ryan, who had $223,000 in his campaign account at the end of last year.

In Florida, Rep. Kendrick Meek, who threw his hat into the ring for the Democratic nomination in January, reported $429,000 on hand at the end of last year.

Democratic Rep. Ron Klein, who is also mulling the Florida Senate race, reported almost $1.6 million in cash on hand.

On the Republican side, both Reps. Connie Mack IV and Vern Buchanan are considering running for Senate. Mack reported just over a half-million dollars on hand at the end of 2008 while Buchanan, a multimillionaire who has proven to be a heavy self-funder, reported just under $100,000 in the bank.

In Illinois, recently appointed Sen. Roland Burris (D) created his fundraising committee last month. Considering the controversy surrounding his nomination, his campaign account will certainly be watched when he begins filing reports later this year.

Rep. Mark Kirk, who is considered a top GOP challenger for the Illinois seat, reported just $79,000 in cash on hand at the end of 2008 after facing a tough re-election last year. Kirk was among the top fundraisers in the House last cycle and he should have no trouble replenishing his coffers if he decides to make a Senate bid.

Another potentially interesting re-election race is that of Sen. David Vitter (R-La.).

Any potential vulnerability that Vitter faces next cycle stems directly from his ties to a Washington, D.C., prostitution ring. Vitter acknowledged that his contact information was among a madam’s records, but he has never admitted to paying a prostitute for sex.

As of Dec. 31, Vitter was sitting on a $2 million campaign war chest while Rep. Charlie Melancon (D-La.), who is often mentioned as a potential Vitter challenger, had $778,000.

Jude Marfil, Liisa Rajala and Charlotte Wester contributed to this report.