Race- and gender-based attacks had backfired in Iowa and New Hampshire. But bread-and-butter negative attacks appeared to have done the trick for the Clinton campaign in Nevada.

Sen. Barack Obama faced a flurry of attacks in the past week -- all baseless, hypocritical and/or disengenous.

The "trillion dollar tax increase on America's hard working families" attack -- a massive distortion of Obama's proposal to end the regressive cap on Social Security taxes, a proposal Clinton has left on the table.

The "hip-deep in financial ties" to nuclear power attack, when Clinton takes nuclear money as well.

The Obama loves Reagan attack -- when both Clintons have said even kinder words about Reagan, and Obama's comments clearly did not embrace Reagan's policies or ideology.

But Obama neither responded fast enough, or countered by going on his own offensive. In turn, the attacks seem to have stuck.

Further, he walked into a Clinton attack point by saying "being president is not making sure that schedules are being run properly or the paperwork is being shuffled effectively," giving Clinton an opportunity to feed a perception that Obama is not prepared to manage the federal bureacracy.

Regardless of the veracity of Clinton's attacks, it is incumbent upon Obama to show he can handle unfair attacks. Because it's not nicieties that await the Democratic nominee in the general election.

Moreover, he needs to show he can aggressively draw contrasts and define the terms of debate.

Merely making a positive case for oneself is not enough in a competitive two-person race against an attack-happy opponent.

It looks as if Obama wants to step up the criticism that Clinton doesn't talk straight.

There's certainly an opening for that. But Obama might also consider sharpening the foreign policy criticism.

Obama has always stressed Clinton's Iraq war authorization vote, and to lesser extent, her vote to designate part of Iran's military as a terrorist organization, to say she would not provide a clean break of Bush's foreign policy.

He could make that a three-pronged attack by adding in Clinton's support of Pakistan's dictator Pervez Musharraf back in 2007, in response to Obama's pledge to act on solid intelligence and strike Al Qaeda if Pakistan refused.

Altogether, Obama can make the case the Clinton has not displayed the foreign policy judgment to make her "Ready on Day 1" to be president, turning the tables on the current narrative.

Obama is being battle-tested like he never has before. Let's see he how handles it.