Sen. Herb Kohl (D-Wis.) sent a strong message when the first fundraising reports of the year were filed Monday, making it clear with a $1 million campaign loan that he will seek re-election.

But others on retirement watch, including Sens. Daniel Akaka (D-Hawaii), Jon Kyl (R-Ariz.) and Jim Webb (D-Va.), offered no indication they will run again in 2012. 

Akaka, 86, raised less than $2,000 in the fourth quarter and had just $66,000 in the bank as of Dec. 31, though he had similar numbers to start his 2006 re-election campaign. Webb raised about $13,000, leaving Democrats hoping that at best he has yet to make up his mind. Kyl’s year-end report was not publicly available at press time, keeping speculation about his potential retirement on the front burner. 

The fundraising figures for Oct. 1 to Dec. 31 offered the first evidence of how well-prepared 33 Senators and their potential challengers are for the long slog ahead. So far there have been three retirements, and several top Republican recruits are already stepping up to challenge Democratic incumbents, including Sen. Claire McCaskill (Mo.), who began this year with a $905,000 campaign chest. 

But it is just the beginning of a 22-month campaign that will be molded by external factors such as the economy and the downballot effect of the presidential election and by internal factors such as retirements, recruitment, primaries and fundraising.

Webb remains one of the biggest unknowns of the 2012 cycle, with insiders from both parties left guessing what he will do. Webb emphasized to reporters last week that this was an eight-year commitment, and that his plan remains to have a decision by March 31. He could face a rematch with former Sen. George Allen (Va.), who has already declared his candidacy but must first get through a GOP primary.

If Akaka runs, he could face former Gov. Linda Lingle (R), whose past fundraising abilities and election success would make it a tough race in Democratic-leaning Hawaii. 

Polling continues to indicate that Sen. Ben Nelson (Neb.), another potential retiree, could be in trouble. But the second-term Democrat raised $81,000 in the fourth quarter and has almost $1.5 million in the bank. No fundraising numbers were available for top Republican candidate Jon Bruning, the state attorney general, who did not file a statement of organization until last month.

Kyl, the Minority Whip, would be an early favorite for re-election if he decides to run. But should he opt out, attention would immediately turn to Rep. Jeff Flake (R-Ariz.), who reported $628,000 in cash on hand. And Democrats would no doubt step up their efforts to recruit a top-tier candidate if it opens up.

While retirements are one of the biggest questions at the beginning of each election cycle, both parties are keenly aware of how much the overall Senate landscape can change in the course of a year — or even a few months.

At this time two years ago, Democrats were cruising into the 2010 cycle with what appeared to be several competitive pickup opportunities, including GOP open seats in Missouri, Ohio and Florida and another likely open seat in New Hampshire. Arlen Specter was a Republican Senator in Pennsylvania, and now-Sen. Pat Toomey (R-Pa.) was believed to be eyeing a gubernatorial bid.

Republicans ended up winning all of those races, as well as a seat in Massachusetts in a January 2010 special election. Democrats won two of their three seats that were deemed the most vulnerable at the beginning of the cycle: Connecticut and Nevada.

Republicans like their odds heading into 2012, with Democrats defending 23 seats compared with the GOP’s 10. And early recruiting successes in competitive states have further boosted GOP optimism.

“Strong Republican candidates are already stepping forward in key races around the country, and Democrats in competitive states are quickly finding themselves on the defensive for their reckless spending record of the last four years,” National Republican Senatorial Committee spokesman Brian Walsh said. “We still have a long way to go until Election Day though, and no one on our side is taking anything for granted. But clearly Republican momentum from November 2010 has carried over into the 2012 cycle and we are focused on winning back a Senate Republican majority next year.”

Democrats, though, caution that they were expected at the beginning of the cycle to pick up seats last year and instead lost seven.

“Republican primaries cost them Senate seats last cycle, and there’s no question it could happen again,” said Eric Schultz, spokesman for the Democratic Senatorial Campaign Committee. 

Schultz held up the example of then-Rep. Mike Castle, who was considered a shoo-in to pick up a Democratic-held seat in Delaware last cycle until his upset in the GOP primary by a tea-party-backed candidate.

“Time after time, Republicans nominated unelectable candidates. It’s far too early for Republicans to declare any victories. Just ask Mike Castle,” he said.

Democrats’ top opportunity to play offense this cycle appears to be in Massachusetts, though Sen. Scott Brown (R) raised $734,000 last quarter and has more than $7 million on hand.

Democrats already have two open seats they will be defending — one of which appears to be a difficult hold.

Sen. Kent Conrad (D-N.D.) is one of the three incumbents to announce their retirements so far, opening up a seat in a very Republican-friendly state where the Democratic bench is thin at best. State Public Service Commissioner Brian Kalk (R) is exploring a bid, and several more Republicans in the state could run, including Rep. Rick Berg. No Democrats have announced bids.

The retirement announcement by Sen. Joe Lieberman (I-Conn.) set off a Democratic primary battle that will include at least one Congressman. 

Connecticut Reps. Christopher Murphy and Joe Courtney could face off in a Democratic primary, with Murphy already running and Courtney considering it. Murphy, who won a competitive re-election race last year, had just $30,000 to start the year, while Courtney had $236,000. Whoever wins the Democratic primary is likely to be favored in the general election in the heavily Democratic state, although Republicans say they plan to target the state and make the race competitive. 

Sen. John Ensign (R-Nev.) maintains that he is running for re-election, but more legal fees and little fundraising left him with just $225,000 at the end of December — not a strong position for an embattled incumbent. Potential rivals Reps. Dean Heller (R) and Shelley Berkley (D) had $815,000 and nearly $1.1 million, respectively.

As Roll Call reported Monday, Rep. Denny Rehberg (R-Mont.) will announce Saturday his challenge to Sen. Jon Tester (D), who is among several from the class of 2006 that are facing top challenges next year. Both had just more than $550,000 in the bank to start the year, and insiders in the state are expecting a spending spree by the candidates and outside groups in what is expected to be one of the cycle’s marquee races.

Looking to escape the same fate that former Sen. Bob Bennett (R-Utah) suffered last year, Sen. Orrin Hatch (R-Utah) raised $416,000 last quarter and has more than $2.5 million in the bank. Rep. Jason Chaffetz (R), a potential convention/primary challenger, started the year with $140,000 on hand.

Mackenzie Weinger and Erin Mershon contributed to this report.