Rehberg, McKinley and Jones voted against last year's GOP budget as well — Rehberg and McKinley said the Medicare changes were too dramatic, while the libertarian Jones argued the bill didn't go far enough with cuts to government. 

Rehberg is running for the Senate in a state with a large senior citizen population, while McKinley represents a district with many seniors and a fiscally populist streak.

This time the centrists were joined by Gibson, a moderate who faces a tough race this fall, and Platts, a centrist who is retiring this year and has been criticized by right-wing groups in the past.

The other Republicans who voted against the bill come from safely Republican districts and seem to have voted against the bill from the right — many of them voted for the more conservative alternate budget proposed by the Republican Study Committee.

Rep Ron Paul (R-Texas) is on the presidential campaign trail and did not return for the vote.

Democrats blasted Republicans for backing last year's House GOP budget and wasted no time doing the same this year. The Democratic Congressional Campaign Committee (DCCC) immediately sent out press releases targeting Republicans in tough races.

"Representative Sean DuffySean Patrick DuffySean Duffy, Rachel Campos-Duffy expecting their ninth child Cheney's advice to daughter: 'Don't screw it up' Senate bill seeks to bring freedom back to banking MORE (R-Wis.) has once again chosen to side with millionaires and billionaires and end the Medicare guarantee that Wisconsin seniors paid a lifetime to earn,” said DCCC spokesman Jesse Ferguson in one statement. “Duffy’s misplaced priorities would raise seniors’ health care costs to protect millionaires, Big Oil, and companies that ship American jobs overseas. Wisconsin voters will remember Duffy’s vote to end Medicare and will hold him accountable.”

Republicans who've taken heat for last year's vote were put in a tough position: either vote again for a similar measure and take additional heat, or vote against a more centrist bill and risk being called a flip-flopper. Most chose to double down rather than flip.

— Updated at 4:21 p.m. and 4:29 p.m.