Sen. Herb Kohl (D-Wis.) reported no fundraising activity in the first quarter of this year.
But he loaned his campaign account $1 million late last year, which was seen as a sign that he'll run for a fifth term.
The Wisconsin Democrat did spend $42,000 on polling during the first quarter, according to a report filed with the Federal Election Commission. Kohl spent just more than $51,000 during the first three months of 2011 and reported $953,000 cash on hand.
National Democrats anticipate Kohl will run again in 2012, and Democratic Senatorial Campaign Committee Chairwoman Patty Murray (Wash.) told reporters last week that she's confident there are no more looming Democratic retirements.
Five members of the Democratic caucus have announced they're retiring next year, leaving the party with 23 seats to defend. Republicans, if President Obama wins reelection, will need a net gain of four seats to win control of the upper chamber.