In Clear Lake, IA, the city where the music died, the Clinton hits on Barack Obama just kept on coming. One month to the day before the Iowa caucuses — and in the Surf Ballroom where Buddy Holly, Ritchie Valens, and the Big Bopper played their last concert in 1959 — Hillary bopped Obama on health care (his plan leaves out 15 million Americans), Social Security (he’s repeating Republican talking points by saying it’s in crisis, and would institute a $1 trillion tax hike), and Iran (he failed to show up for that important vote to call the Revolutionary Guard a terrorist group, but later used it to attack her).

But there were some new wrinkles today, including taking Obama to task for voting not “yes” or “no,” but “present” 7 times as a state senator in Illinois on issues like abortion and gun violence.

“A president can’t pick and choose which challenges he or she will face,” she said. “Instead of looking for political cover or taking a pass, we need a president who will take a stand.”

Without mentioning him by name, Hillary also dismissed the Obama argument that her long tenure in Washington makes her ill-equipped to bring about real change — saying “you decide what makes sense – entrust our country to someone who is ready on day one to make the decisions and the changes we need, or to put America in the hands of someone with little national or international experience who started running for president has soon as he arrived in the United States Senate.”

Obama’s campaign responded with a long list of press clippings defending those “present” votes. Obama spokesman Bill Burton released a statement saying “The truth is, Barack Obama doesn’t need lectures in political courage from someone who followed George Bush to war in Iraq, gave him the benefit of the doubt on Iran, supported NAFTA and opposed ethanol until she decided to run for President.”

And asked about the increasing frequency of the attacks, Obama replied, “it’s silly season.”