Senate Republican Policy Committee Chairman John Thune (S.D.) warned Tuesday that GOP distrust of Democratic leaders runs so deep that even if Democrats abandon plans for a comprehensive health care reform bill in favor of smaller fixes, there is no guarantee of Republican support.

In a conference call with reporters, Thune argued that an incremental approach to health care reform is “the only way to end up with a bipartisan bill.— But he warned the greatest hurdle to such a solution could end up being Republicans’ unwillingness to trust Democratic leaders to not use the conference process to rewrite a rifle-shot bill into a fully comprehensive bill.

“The question is, at the end of the day, if Republicans come on board with something that is incremental, will it stay that way?— Thune said, adding that it “remains to be seen if [Democrats] are willing to come to that position.—

At the same time, with public opposition to comprehensive reform continuing to grow, Republican leaders seized on new federal budget deficit projections to argue comprehensive legislation will bankrupt the country. The White House Office of Management and Budget announced Tuesday morning that the 10-year budget deficit was projected to reach more than $9 trillion.

“The Obama administration’s announcement that the 10-year federal deficit has risen to $9 trillion is staggering. We’re on track to double the national debt in five years and triple it in 10 years. This is a flashing red light for any health care proposal that doesn’t reduce the cost of health care for Americans and their government,— Republican Conference Chairman Lamar Alexander (Tenn.) said in the same conference call.

Despite efforts by the Obama administration, outside organizations, and Democrats to rebuild support for their comprehensive reform efforts, public skepticism remains high, and at least two key lawmakers this weekend urged the administration to abandon a comprehensive approach — at least for now. Sens. Joe Lieberman (ID-Conn.) and Dick Lugar (R-Ind.) — both of whom are key to Democrats’ dwindling hopes of cobbling together a bipartisan compromise that can win 60 votes — said that public opposition has grown to the point that a comprehensive approach is likely not possible and called for a smaller set of reforms.