ABC News’ Rick Klein reports: The Democratic establishment may be lining up behind Sen. Arlen Specter — but some who control the ground troops aren’t so ready to fall into line. On today’s "Top Line," Richard Trumka, the secretary-treasurer of the AFL-CIO, warned that union leaders may drop their longstanding support for Specter, D-Pa., if — as he has promised to do — he votes against them on their legislative priority, the Employee Free Choice Act. "Those decisions will be made by people in the state, and our members in the state know who will stand with them. And if Arlen Specter — he stood with them in the past — if he continues to stand with them, they’ll support him. If he doesn’t, they won’t support him," Trumka told us. Trumka said the Democratic Party establishment won’t prevent labor leaders from making their own decision on Specter, even though President Obama, Vice President Joe Biden, and Gov. Ed Rendell, D-Pa., have all pledged to support Specter. "We have a lot of members that are elected into that establishment, and our members generally do what’s right by workers, and we don’t care who’s lined up against us," Trumka said. "If a candidate isn’t good for workers, we won’t be there. If they are good for workers, we will be there regardless of their party. I mean, we supported Arlen Specter — and he was a Republican — because he was good for what was happening. He was good for our members at that time." Specter last week switched his party affiliation and became a Democrat, citing the likelihood that he would lose in a GOP primary next year. But Specter has said he continues to oppose the Employee Free Choice Act — the pro-unionizing bill known as "card-check" by its opponents — even though he supported it in the previous session of Congress. "I said when I made the switch, I’m still against that bill," Specter said Sunday on NBC’s "Meet the Press. "Democrats are all for it; Republicans are all against it, and I’m the critical vote." Though leading Democrats welcomed Specter and offered their support, others — including Rep. Joe Sestak, D-Pa. — are still considering primary challenges to Specter, giving labor leaders somewhere else to direct their resources, should they so choose. Trumka said he’s still confident that Specter’s concerns about the bill can be addressed. "He says he’s not for the current bill in its current form, although I think there is a form that he will [support]. We’ll see what happens," he said. He added that any bill "absolutely" would have to provide for binding arbitration to provide a fixed timeline for resolving disputes over forming unions — a provision that is harshly opposed by business groups. "This would take some of their ability to intimidate and delay away," Trumka said. Asked whether the measure will get the votes of at least 60 senators, Trumka said, "Yes we will." Click HERE to see our interview with Richard Trumka. Also today, we chatted with Jan Crawford Greenburg, who covers the Supreme Court for ABC News, about the early skirmishing over the court vacancy, and about how the Senate Judiciary Committee’s Republican side is likely to operate if Sen. Jeff Sessions, R-Ala., is the top GOP member. Click HERE to see the full interview with Jan Crawford Greenburg.