Governor Mitt Romney’s debate performance last night has probably reenergized his campaign and given conservatives something to crow about after a month of mostly bad news. And President Obama, who often seemed intent on being restrained, is the purported loser in the first presidential debate, according to early polls.

But Republicans shouldn’t get too cocky and Democrats shouldn’t run for cover like they so often do in moments like this. Obama supporters might recall then-Senator Hillary Clinton clobbering the president more than once in the Democratic Primary in 2008.

That said, there were a couple moments that defined the candidate’s ideological differences. One involved taxes, but even more revealing was the discussion about the future of Medicare.

When Obama looked into the camera and told 54 year-old Americans to pay attention, let’s hope they were. He might better have given that advice to Americans between 40 and 54, since Romney’s Medicare voucher plan will have a serious and fairly immediate impact on the lives of a much larger swath of Americans. Converting the Medicare system to a voucher plan would be a windfall for the insurance industry and could effectively kill the program.

Obama failed to press Romney on what happens when the voucher either doesn’t keep pace with the cost of health care, or the coverage it could purchase is too limited to protect seniors.

Debates come and go, but changing Medicare to a voucher plan would be a tragedy for future seniors.