Will the GOP lose its nerve on Medicare reform?

Eager to press their advantage, Senate Democrats will stage a vote on the Medicare plan as soon as Wednesday, forcing Senate Republicans into a yes-or-no choice that both sides know will become the basis of countless campaign commercials over the next year and a half.

It is still a long way to Election Day 2012, the underlying problem of a long-term fiscal imbalance remains as pressing as ever and Democrats face divisions and messaging problems of their own.

But after a 2010 election that seemed to signal not only a Republican resurgence but also a rejection of big government and a need for bold, Tea Party-type steps to slash spending, the politics now look a whole lot more complicated. Both parties are being reminded anew that voters like the idea of budget cuts, but that they often recoil when those cuts threaten the programs that touch their lives.

While well aware that there were political risks, many Republicans went into this year convinced that the rapid growth of the national debt had changed the public mood when it came to tackling the entitlement programs, starting with Medicare, the biggest driver of projected future deficits. In an ambitious budget plan written by Representative Paul D. Ryan of Wisconsin, chairman of the House Budget Committee, House Republicans embraced a proposal that would convert Medicare into a subsidized program for the private insurance market.