In a sign of how hard it is for Democrats to regroup on major health care legislation, two centrist Democratic senators said on Tuesday that they would oppose efforts to muscle through a bill using a procedural tactic called budget reconciliation.

Senator Blanche Lincoln, Democrat of Arkansas, who is in a tough race for re-election this year, said, “I am opposed to and will fight against any attempts to push through changes to the Senate health insurance reform legislation by using budget reconciliation tactics that would allow the Senate to pass a package of changes to our original bill with 51 votes.”

Brendan Smialowski for The New York Times

Mrs. Lincoln added, “I have successfully fought for transparency throughout Senate deliberations on health care, and I will continue to do so. I will not accept any last-minute efforts to force changes to health insurance reform issues through budget reconciliation, and neither will Arkansans. We have worked too long and too hard on this reform effort – we need to get it right.”

And Senator Evan Bayh, Democrat of Indiana, who is also on the ballot in November, said he would counsel against using reconciliation to push past Republican opposition.

“It would destroy the opportunity, if there is one, for any bipartisan cooperation the rest of this year on anything else,” Mr. Bayh said.

Ms. Lincoln said she would continue fighting for health legislation. “If the House chooses not to pass the Senate bill as is, then I will work with my colleagues, both Democrats and Republicans, to identify the basic reforms that we can agree on,” she said in a statement. “I hope that our efforts going forward will be truly bipartisan, because the high-pitched, partisan tone in Washington is not creating jobs, nor is it solving the health care challenges facing every American, whether it be cost or access.”