Alexi Giannoulias to formally announce run for US Senate, sources say

A spokesman says that State Treasurer Alexi Giannoulias will make a formal announcement sometime next week about plans to run for the United States Senate.

Giannoulias is not yet an official candidate, but he picked up another endorsement Sunday. Congressman Mike Quigley threw his support behind the Democrat. Quigley joins a growing list of elected leaders supporting Giannoulias.

The jockeying ahead of the February primary election continued Tuesday as first-term state Treasurer Alexi Giannoulias said he will kick off his Democratic U.S. Senate bid this weekend, and a twice-vanquished Democratic congressional candidate announced he'll run again on the North Shore.

Giannoulias' campaign for the Senate seat being given up by embattled appointee Sen. Roland Burris had been expected after the wealthy banking heir raised more than $1.8 million. Giannoulias has called President Barack Obama a mentor, and Obama helped him win the treasurer's office in 2006 by backing him against the party-favored Democratic candidate.