So even though Democratic Sens. Bill Nelson (Fla.), Amy Klobuchar (Minn.), Bob Menendez (N.J.), Sherrod Brown (Ohio) and Maria Cantwell (Wash.) as well as Republican Sen. Scott Brown (Mass.) have considerable financial advantages now, none of them can rule out a competitive race next fall.
Democratic strategists are working with Senators who have growing war chests and no declared opponents to "strike the right balance" in their campaign spending.
"The old premise is that you raise a ton of money and save every last penny until the very end," current DSCC Executive Director Guy Cecil said. "Now, wisely investing in infrastructure in the off-year can save you money in the long run."
Even with increased media attention and scrutiny on Senate recruiting, there is still time for each party to get candidates into key races. Of those 16 successful Senate challengers over the past decade, 12 weren't even in the race at this point in their cycles.
Some of those eventual candidates, such as Jeanne Shaheen (D-N.H.) and John Thune (R-S.D.), already had statewide profiles and could afford to delay their entry. But many of them, including Johnson, Kay Hagan (D-N.C.), Jim Webb (D-Va.) and Jeff Merkley (D-Ore.), had low statewide name identification when they began their races.
Then-Rep. John Boozman (R) hadn't yet entered the Arkansas Senate race at this point in the 2010 cycle, but he went on to defeat Sen. Blanche Lincoln (D) in the general election, spending only a quarter of the money she spent in the process. Both candidates spent money in competitive primaries, and Boozman didn't need much to ride the electoral wave to victory in the general election.
Not only were Hagan, Merkley and Webb not yet in the race, they used only half the cash spent by the Senators they defeated.
Democratic strategists are quick to point out Sen. Debbie Stabenow's (D) early positioning in Michigan. She had
$3 million in the bank through March and no challenger, but Stabenow well understands the limits of those assets.
Almost a dozen years ago, GOP Sen. Spencer Abraham was shattering previous fundraising records in Michigan. He held a cash advantage of $3 million to $860,000 over Stabenow, then a Member of the House. Sixteen months later, Stabenow defeated Abraham in a very close race.
In fact, of the five GOP incumbents featured in a July 1999 Roll Call article about Senators turning in a "strong six months of fundraising," including Abraham, only Santorum survived.
Comparing financial figures between incumbents and challengers is too simple because it fails to take into account spending by outside groups. Even a dozen years ago, Stabenow spent about 60 percent of Abraham's total but benefited from an influx of money from EMILY's List, the Democratic abortion rights group.
"You don't have to go dollar for dollar," Poersch said. "But it helps that someone else is at the table."
Even when Democratic challengers were being outspent in 2006 and 2008, the DSCC was consistently dropping more money on races than its GOP counterpart.
And when challengers are matching an incumbent in fundraising early, that doesn't guarantee a Senator's defeat.
In 2008, then-Rep. Tom Allen (D) stayed competitive with Republican Sen. Susan Collins in fundraising throughout the race, but it wasn't enough to defeat her.