Flake's ad attempts to illuminate what it characterizes as unexamined aspects of Carmona's past by focusing in on his time as CEO of the Pima County healthcare system.

The ad says that while Carmona was CEO, the Pima County healthcare system debt increased by 28 percent in one year, to $46 million dollars, and that Carmona was "forced to resign."

"Richard Carmona, another Obama big spender," it closes.

This is largely a new attack from the Flake campaign, which has up until now focused on tying Carmona to President Obama in a state in which Mitt Romney has consistently posted a lead on the president.

Carmona spokesman Andy BarrGarland (Andy) Hale BarrElection Countdown: Family separation policy may haunt GOP in November | Why Republican candidates are bracing for surprises | House Dems rake in record May haul | 'Dumpster fire' ad goes viral Cook Political Report shifts two House race projections toward Dems GOP super PAC targets House districts with new M ad buys MORE called the ad misleading.

"Dr. Carmona managed a hospital which was largely responsible for indigent care," he said. "The budget was not managed by him but by the Pima County Board Supervisors and he told them that the money allotted would not match the care that they wanted."

He added that the issue had already been addressed when Carmona went through confirmation hearings to become U.S. surgeon general, and that despite scrutiny from the Senate, he was unanimously confirmed.

Carmona's campaign released an ad on Friday as well, contrasting what it characterizes as his "life's work" with Flake's record in Congress.

"As surgeon general, Rich Carmona put aside politics to do what's right, because saving lives has been his life's work," a narrator says over shots of Carmona interacting with children. It adds that Carmona will protect Medicare in Congress.

The ad then shifts to a more negative tone and charges that Flake "voted to end traditional Medicare" and to force seniors to pay double for their care, adding that Flake is "just not for us."

Flake spokesman Andrew Wilder, in response, tied Carmona to Democratic policies and accused him of "Mediscaring" seniors.

"The hard fact is that Democrats like Richard Carmona support the status quo, which will lead to Medicare’s bankruptcy. Worse, Carmona supported the Democrats’ cut of $716 billion from Medicare program in order to pay for President Obama’s massive new health care law. That’s just wrong," he said in an email to The Hill.

The argument that Carmona is able to work across the aisle is one his campaign will have to win in advance of Election Day if it hopes to succeed. Though Carmona has run a strong campaign thus far, keeping within single digits of Flake in most recent polls, it will be difficult for the Democrat to shake Obama's unpopularity in the state.

Thus far, that's been Flake's main argument — that Carmona would be a "rubber stamp" for Obama's agenda. But the shift in attacks signified by this new ad may indicate that the rubber-stamp label isn't sticking for the candidate who served as U.S. surgeon general under former President George W. Bush.

That, coupled with the fact that both the National Republican Senatorial Committee and the Democratic Senatorial Campaign Committee launched ad buys there over the past two weeks, is reflective of the fact that this is one of the most competitive races in the nation.

--This post was published at 11:10 a.m. and updated at 1:19 p.m.