Congresswoman Tammy Duckworth picks up a big endorsement in his bid for U.S. Senate, and focuses her attacks on the Republican incumbent, not her primary rivals.

Services Employees International Union (SEIU) is backing Duckworth’s bid in the Senate race over two Democratic primary opponents: State Sen. Napoleon Harris (D-Harvey) and former Chicago Urban League president Andrea Zopp.

SEIU Illinois Council President Tom Balanoff says the union did meet with Zopp, but not with Harris, arguing he entered the race too late.

“I don’t want to say anything necessarily bad about Andrea, she’s (had) a lot of public service, or Napoleon, he has a pretty good voting record in Springfield,” Balanoff said, “but when we looked at everything, we felt that Tammy not only had the record, but  had the story.”

Duckworth herself didn’t mention her primary rivals, instead focusing on her potential general election opponent, U.S. Sen. Mark Kirk (R-Ill.), attacking his support of tax cuts as well as free trade agreements like the Trans-Pacific Partnership.

“He calls himself an ardent free trader, and make no mistake, blind support for free trade instead of fair trade has devastated families and communities across this state,” Duckworth said.

SEIU wasn’t likely to support Kirk given his close ties to Gov. Bruce Rauner, who has been the target of negative ads from the union over budget cuts.

Duckworth, however, said she doesn’t plan on bringing Rauner’s name into the Senate race should she win the Democratic nomination.

“As far as Mr. Rauner is concerned, I’m sure he’ll hit the news on his own without my help,” Duckworth said.

Kirk campaign manager Kevin Artl alluded to the battle over Rauner’s agenda on the state level in reacting to the endorsement, saying in a statement, “While SEIU and Rep. Duckworth continue their partisan efforts to raise taxes on Illinois families while blocking reform, Senator Kirk chooses a different path by serving as an independent-minded, reform driven leader who is delivering results.”