Year-end fundraising reports filed this week only confirm what strategists from both parties already know — this fall’s battle for control of the Senate is going to be close.

Scan the playing field state-by-state, region-by-region, and it’s hard to reach a different conclusion. Both parties have solid arguments for why they’ll finish on top, and the latest money figures only solidify them.

Democratic incumbents from the class of 2006 are fundraising as if they’re running for the first time, party insiders said, while Republicans see several paths to net the four seats needed for a majority.

“As much as I would like to believe that 2012 will be a wave election for Republicans, it is unlikely to be so at the presidential level,” said Scott Bensing, a former executive director at the National Republican Senatorial Committee. “It will be close, meaning that high-quality Senate candidates and well-run campaigns will win the day.”

Bensing, who now runs SB Strategic Consulting, said the Democratic Senatorial Campaign Committee “is fighting on too many fronts, has too many retirements and Republicans have a great slate of candidates,” including an incredibly well-funded incumbent in Massachusetts and a former governor in Hawaii who has made that the mostly unlikely race of the cycle.

Democrats entered the 2012 cycle with a disparate number of seats to hold, 23 to the GOP’s 10. But, as DSCC Chairwoman
Patty Murray (Wash.) said in December, the party feels a lot better about its chances of holding the majority than it did a year ago.

“It’s no secret our side has more seats to defend, and the DSCC has made sure our candidates have their campaigns in order,” said Democratic strategist Jef
Pollock of the Global Strategy Group.

“They’ve also expanded the playing field with good recruiting in Arizona and gone a long way toward picking up Massachusetts,” he added. “So we have reason to be optimistic about how things will turn out when the American people choose which party they want leading the country.”

While Republicans remain the favorites to win them, the potential competitiveness of North Dakota and Arizona,  where Sen. Jon Kyl (R) is retiring, is a positive development for Democrats.

Democrats recruited former North Dakota Attorney General Heidi Heitkamp to run for retiring Sen. Kent Conrad’s (D) seat and former Surgeon General Richard Carmona to run against Rep. Jeff Flake, or whoever emerges from the GOP primary in Arizona. Carmona and Heitkamp turned in fundraising quarters rivaling Flake and Rep. Rick Berg (R-N.D.), despite not entering their respective races until early November.

In Massachusetts, Harvard professor Elizabeth Warren rode a wave of national star power to cut into the seemingly insurmountable cash advantage of Sen. Scott Brown (R). Warren raised a remarkable $5.8 million in the fourth quarter, ending the year with $6.1 million in cash on hand. Brown had a whopping $12.9 million in the bank after a $3.3 million quarter.

Democrats said privately that while they remain confident in Hawaii, former Gov. Linda Lingle’s (R) candidacy has made it a race. The increasingly likely  New Mexico contest between Rep. Martin Heinrich (D) and former Rep. Heather Wilson (R), assuming they win their primaries, is a competitive race mostly flying under the radar.

Roll Call currently rates seven races as Tossups: open Democratic seats in New Mexico, Virginia and Wisconsin; the seats of Democratic Sens. Claire McCaskill (Mo.) and Jon Tester (Mont.); and the seats of Republicans Brown and Sen. Dean Heller (Nev.).

Heller picked up the fundraising pace in the fourth quarter, breaking even in the money race with Rep. Shelley Berkley (D). Both raked in $1.1 million and finished just over $100,000 of each other in cash on hand.

McCaskill, Tester and former Virginia Gov. Tim Kaine continue to outpace their GOP opponents and all have cash advantages of at least $1.3 million. Tester raised nearly twice as much as Rep. Denny Rehberg (R), but that race is expected to remain a virtual tie until the election.

McCaskill ended the year with $5 million in the bank. Among her toughest GOP opponents, Rep. Todd Akin (R) raised $232,000 and had $1.2 million in cash on hand, while GOP businessman John Brunner brought in more than $1.2 million, including a $1 million personal loan, but finished with only $209,000 in the bank.

Kaine and ex-Sen. George Allen (R) are running for the seat of retiring Sen. Jim Webb (D). Kaine is more closely tied to President Barack Obama than any other Senate candidate — Allen hasn’t let that go unnoticed and Kaine hasn’t run from it.

In Wisconsin, Rep. Tammy Baldwin (D) raised $1.2 million last quarter and most likely will face either former Gov. Tommy Thompson or former Rep. Mark Neumann in the general.

The seats of retiring Democratic Sens. Conrad and Ben Nelson (Neb.) are rated as Likely Republican pickups, as are two seats Republicans must hold — the open Arizona seat and Sen. Dick Lugar’s (R-Ind.) spot. Lugar has a primary but raised twice as much as state Treasurer Richard Mourdock and had an overwhelming lead in cash-on-hand with $4 million.

Among the races Roll Call rates as Leans Democratic are Ohio, where Sen. Sherrod Brown (D) and state Treasurer Josh Mandel (R) are in a fundraising arms race; Hawaii, where Rep. Mazie Hirono and former Rep. Ed Case are duking it out for the chance to take on Lingle; Michigan, where Sen. Debbie Stabenow (D) will likely face former Rep. Pete Hoekstra; and Florida, where Sen. Bill Nelson’s (D) fundraising largess continues to make it more unlikely that the NRSC will spend its precious resources in the expensive state.

“It’s continuing evidence that it’s not 2010 anymore, Toto,” SKDK Managing Director J.B. Poersch, a former DSCC executive director, said of Democratic incumbents’ fundraising success.

Republicans agree, saying Democrats shouldn’t expect a replay of the 2010 GOP primaries that helped Democrats keep control of the Senate.

“November is a long way off, but I would much rather be us than them right now,” Bensing said.