Barack Obama will unveil a budget proposal today that the White House has described as its final deficit reduction offer to recalcitrant Republicans. But members of Obama's own party are already protesting the chained-CPI social security cut expected in the budget: Bernie Sanders led a rally outside the White House, 107 members of congress signed a letter urging Obama to reconsider and some 30 members of congress are actively opposing the measure.

The public hostility toward chained-CPI adjustment to cost-of-living increases will pressure more Democrats to break with Obama on this issue, Nation Washington correspondent John Nichols told Tamron Hall on MSNBC's NewsNation.

"I suspect the White House is a little bit surprised by the energy and the speed with which the negative response has come from the progressive community," Nichols said.

—Alec Luhn

Read John Nichols on chained-CPI and why it's quickly becoming a line in the sand for many Democrats.