Congressional Progressive Caucus Co-Chairman Raúl Grijalva (D-Ariz.) said in an interview Tuesday that he will push hard for significant changes to the Senate health care bill in conference but stopped short of saying he would vote to kill it.Grijalva complained that Sens. Joe Lieberman (ID-Conn.) and Ben Nelson (D-Neb.) have threatened to block a conference agreement if the Senate bill is changed in any significant way.Theyve had their way up to this point, he said. For either them or the Senate to expect to send their bill as is through the House is going to be very difficult.Grijalva ticked off a list of items he would like to see addressed, including allowing immigrants to buy in to the new insurance exchanges, repealing the antitrust exemption for the insurance industry, including some form of public aspect to the plan, and moving up implementation of the heart of the bill faster than the 2014 date in the Senate bill.Nelson, however, reiterated Tuesday his threat to bring down the conference report if it departs significantly from the Senate bill. Nelson has specifically rejected the House language allowing illegal immigrants to buy in to the insurance exchanges with their own money. Its a deal-breaker, he said. There is no compromise there that I can see.Nelson also vowed to block the House tax surcharge on the wealthy, labeling it class warfare.Sen. Jay Rockefeller (D-W.Va.), who will be a conferee, said he will be guided by the need to keep the 60 Senate Democrats on board. Theres only a certain amount of wiggle room, he said. Whats the good of having a good conference report that fails in the Senate?Rockefeller said he hopes the math of the Senate will prevail on House Democrats to largely accept the Senate bill. If it doesnt change minds, then this will all have been for naught, he said.Grijalva also said there are a lot of Members who want the same Medicaid deal for their states that Nelson won for his exempting them from paying the costs of the new expansion.