In a move designed to send a message to its donors — but also to women’s groups, liberal Democrats and potential challengers — EMILY’s List announced Wednesday that it was endorsing newly-appointed Sen. Kirsten Gillibrand (D-N.Y.) for re-election in 2010.

In a statement, Ellen Malcolm, president of the powerhouse fundraising group, called Gillibrand “a great advocate for women and families.”

“In Congress, Gillibrand has fought for progressive policies such as equal pay and expanded health care for children.,” Malcolm said. “She has pioneered government accountability and transparency by becoming the first member of Congress to post her schedule online for all to see, and has championed economic development in a region hard-hit by the economic downturn. We look forward to her continued leadership for the people of New York and women across the country.”

The EMILY’s List endorsement comes just one day after Gillibrand was sworn in as a Senator. The former Upstate Congresswoman was appointed Friday by New York Gov. David Paterson (D) to replace Hillary Rodham Clinton, who is now secretary of State.

Despite the blessing of EMILY’s List and Clinton and Sen. Charles Schumer (D-N.Y.), Gillibrand’s appointment has not been universally embraced, and some liberal groups have been particularly critical. Rep. Carolyn McCarthy (D-N.Y.) has threatened to run against Gillibrand in the Democratic primary next year because of Gillibrand’s support from the National Rifle Association, and a group of Latino state legislators said Tuesday that they would try to recruit a primary challenger because of Gillibrand’s stances on illegal immigration.

The support of EMILY’s List will help deflect some of the criticism — and boost Gillibrand’s fundraising.