As he continues to weigh a primary challenge to now-Democratic Sen. Arlen Specter, Rep. Joe Sestak met with Service Employees International Union President Andy Stern on Monday afternoon.

Specter announced last week that he is switching parties so that he can run as a Democrat in 2010, because he didn’t think he could win the Republican primary against former Rep. Pat Toomey. When he was still a Republican earlier this year, Specter voted against invoking cloture on the Employee Free Choice Act, the top legislative priority for organized labor.

Both Sestak’s office and a spokeswoman for the SEIU confirmed the meeting.

“It is one of many meetings that Andy does with Members of Congress to discuss legislative issues that are important to our members,— SEIU spokeswoman Ramona Oliver said.

Sestak has made several media appearances after Specter’s announcement during which he declined to say whether he would challenge Specter, who has the backing of the Democratic Senatorial Campaign Committee and the White House. If Sestak were to run against Specter, having support from unions would be a major boost for his campaign.