The big news in the Democratic U.S. Senate primary today is a new Rasmussen poll showing how the three top contenders are faring in head-to-head matchups against GOP frontrunner Mark Kirk.  After tying Kirk in the October Rasmussen poll, Alexi Giannoulias now leads him by three points.  Meanwhile, both Cheryle Jackson and David Hoffman trail him -- but by less than in the last survey.  Here are toplines (with the October results in parentheses):

Giannoulias: 42% (41%)
Kirk: 39% (41%)
Undecided: 15% (13%)

Jackson: 39% (39%)
Kirk: 42% (43%)
Undecided: 15% (13%)

Hoffman: 38% (33%)
Kirk: 42% (43%)
Undecided: 17% (16%)

The poll didn't measure the latest primary standings, but showed that Jackson and Hoffman continued to grow their name identification.

In other news, the Sierra Club announced their endorsement of Giannoulias:

"Alexi Giannoulias has been a principled leader on environmental issues as Treasurer and we are excited to be supporting his run for the U.S. Senate," said Jack Darin, director of the Illinois chapter of the Sierra Club. "He is the only candidate to promote economic policies that will not only put people back to work, but will create the clean energy jobs of the 21st Century."

Also of note, Giannoulias is holding a press conference this weekend at which he will call for renegotiating the North American Free Trade Agreement (NAFTA) and offer a plan "to curb outsourcing and pressure China to end its unfair trade practices."  Stay tuned for more details on Monday.

Full Disclosure: The SEIU Illinois State Council, which sponsors this website, has endorsed Alexi Giannoulias in the Democratic primary for U.S. Senate.