Top Senate Democrats tried to scotch efforts by Majority Whip Richard Durbin to include Social Security in comprehensive deficit-reduction negotiations, illustrating the challenge facing the bipartisan talks…

If Democratic negotiators are forced to take Social Security out of the discussions, Republicans could counter by refusing to discuss tax changes that raise revenue. With only Medicare and Medicaid left, talks would likely collapse, said Erskine Bowles, a former Clinton White House chief of staff who co-led Mr. Obama’s deficit commission last year. Limiting the scope of negotiations “is the exact wrong thing to do,” Mr. Bowles said.

Sen. Tom Coburn (R., Okla.), one of those involved in the bipartisan talks said “purists on both sides” need to abandon their entrenched positions. For Republicans, that would mean ending or limiting hundreds of tax deductions and exemptions. For Democrats, the issue is Social Security. “For a deal to happen, Social Security needs to get fixed,” Mr. Coburn said.

Sens. Reid and Schumer want any talk of changes to Social Security to be dealt with separately from the broader deficit-reduction talks.