As Gen. David Petraeus testified Tuesday on Capitol Hill about significant but "reversible" improvements in Iraq, the hearing room also served as a proxy debate site for the candidates to argue for their respective policies.

Arizona Sen. John McCain was the first of the three major presidential candidates to get a turn questioning Petraeus and Amb. Ryan Crocker, and used his opening remarks in a Senate Armed Services Committee hearing to praise the progress that has occurred in the last year.

Barack Obama, from his junior post on the Senate Foreign Relations Committee, did not testify until late in the afternoon, but he used the opportunity to press Crocker and Petraeus to find an acceptable endpoint to the Iraq war. He suggested that endpoint could be a "messy, sloppy status quo."

"I continue to believe that the original decision to go into Iraq was a massive strategic blunder," Obama said, while still praising the two men for "cleaning up the mess" and praising the troop surge for helping to reduce violence.

In lamenting the country's "overstretched" economic and military resources, Obama repeated his call for a troop withdrawal timetable -- one that comes after the military reaches a "manageable situation" with regard to Iranian influence and Al Qaeda in Iraq.

"I'm trying to get to an endpoint. That's what all of us have been trying to get to. The problem I have is that the definition of success is so high," he said. Obama said a goal of erecting a "highly effective Iraqi government" and completely eliminating Al Qaeda in Iraq "portends the possibility of us staying for 20 or 30 years."

"If on the other hand our criteria is a messy sloppy status quo but there's not huge outbreaks of violence ... it's not a threat to its neighbors and it's not an Al Qaeda base, that seems to me an achievable goal within a measureable time frame," he said.

Democratic rival Hillary Clinton, who spoke earlier in the day, said that the multiple and extended deployments are taking a toll not only on U.S. soldiers but on security policy, since troops are not available to engage in other actions.

"We rarely talk about the opportunity costs and the opportunities lost because of the continuation of this strategy. The longer we stay in Iraq, the more we divert resources not only from Afghanistan but other international challenges as well," Clinton said before questioning the witnesses about the standards being applied to determine a conditions-based withdrawal.

"I think it's time to begin a orderly process of withdrawing our troops, start rebuilding our military and focusing on the challenges posed by Afghanistan and global terrorist groups and other problems that confront America," she continued.

The appearance of Petraeus and Crocker served as an opportunity to play out this season's election drama over the best approach to deal with Iraq. McCain and Clinton are members of the Senate Armed Services panel that first heard from the military and diplomatic leaders.

McCain, the ranking Republican on the committee, said in a statement delivered ahead of the leaders' progress report that the U.S. can capitalize on successes of a recent surge if it demonstrates patience and support for troops' efforts.

"This means rejecting, as we did in 2007, the calls for a reckless and irresponsible withdrawal of our forces at the moment when they are succeeding. I do not want to keep our troops in Iraq a minute longer than necessary to secure our interests there. Our goal -- my goal -- is an Iraq that no longer needs American troops. And I believe we can achieve that goal, perhaps sooner than many imagine. But I also believe that to promise a withdrawal of our forces, regardless of the consequences, would constitute a failure of political and moral leadership," he said.

Part of McCain's testimony was interrupted by an anti-war CodePink demonstrator who held up a banner and shouted, "Senator McCain, there is no military solution." Committee chairman Carl Levin banged his gavel and warned that if the shouting continues demonstrators in the audience will be thrown out.

"I have had this experience previously, Mr. Chairman," McCain said with a half-hearted laugh.

Both Levin and Sen. Joe Biden, chairmen of the Senate Foreign Relations Committee, said beforehand that the hearings would not be used as a commander in chief dress rehearsal and the candidates would not be given any special attention or be treated differently than any other senator.

Afterward, Levin said he thought the hearing wasn't overly imbued with presidential politics.

"I thought it was actually a very, very level hearing, and that it was -- that the tone of it was right. And I saw a minimal amount of presidential politics. I know that there's an understandable focus because Senators Clinton and McCain are there. But I thought that -- I think people went really to the substance and avoided politicizing this hearing in any way," he said.

Speaking with FOX News Tuesday morning, Clinton made clear that she does not believe the surge has succeeded in its goal to bring Iraq political progress.

"The fact is the stated purpose of the surge last year was to give the Iraqi government a push by trying to create some space and time for it to make decisions that it had to make. And that hasn't happened," Clinton said, pointing to recent comments by Petraeus that political reconciliation isn't what one would have expected.

Clinton said recent fighting in southern Iraq as well as Sadr City in Baghdad is a result of Iraqis' inability "to move forward."

"The Iraqis I think believe they've been given a blank check by George Bush," Clinton said.

"If I'm president, I will begin to withdraw troops and I will do it carefully and responsibly, but I will make it clear to the Iraqis that there is no military solution. It's up to them,' she said.

In advance of the hearing, the ongoing fight continued between McCain and Obama over the proper meaning of McCain's remarks that he would be willing to stay in Iraq for 100 years in a fashion similar to U.S. troops stationed in South Korea, Japan and Germany.Speaking on NBC's Today Show, Obama said the record is clear that McCain wants to continue an occupation of Iraq. He said if he were president, he would set a timetable to withdraw one to two brigades per month.

"What John McCain was saying was that he is happy to have a potential long-term occupation in Iraq. Happy may be overstating it. He is willing to have a long-term occupation in Iraq, as long as 100 years. In fact, he said 10,000 years, however long it took. That was his argument," Obama said.

"The problem is that there's no end in sight, because John McCain has not offered any clear point at which he suggests it's time for us to move our troops home. And the American people, I think, have recognized that we have a legitimate national security interest in Iraq. They've been extraordinarily patient. Nobody has been more patient than the military families who are there. But at some point, we have to say to ourselves that the Iraqi government has to stand up and make the difference. And they have not done that."

McCain's campaign countered that Obama continues to misrepresent McCain's stance.

"In his book 'The Audacity of Hope,' Obama writes that voters are 'tired of distortion, name-calling, and sound bite solutions to complicated problems.' This is exactly the opposite of what Obama offered this morning," said spokesman Brian Rogers.

Few surprises were expected out of Petraeus and Crocker's testimony. The administration has already announced that the it will reduce the length of troop deployments to 12 months from an extended 15.

The number of brigades in Iraq in July is also expected to drop to 15 -- equal to the 140,000 or so who were there before last year's surge.

The two also were lobbying for more cash to fund operations on the ground. Congress has not yet acted on President Bush's request to add an additional $100 billion or so to run Iraq operations through September.

However, the Clinton and Obama campaigns have been closely involved in crafting Democratic strategy over financing the war, and could make a big deal about claiming the fighting in Basra is a civil war that requires U.S. troops to step back. That kind of appeal could work on moderate Republicans like Sens. John Warner and Dick Lugar.

Democrats are also looking to exploit the funding divide, noting that the U.S. is spending at a ratio of about 11 to 1 on reconstruction in Iraq.

McCain pre-empted some of that argument, noting that while the Iraqi government builds its bureaucracy to disburse its revenues, they might start "contributing significantly" to the Commander's Emergency Response Program (CERP), which pays for employment and reconstruction projects throughout the country.

Iraqis "need to move a portion of their growing budget surpluses into job creation programs, move toward an end to their reliance on outside sources of aid and look for other ways to take on more of the financial burdens currently borne by American taxpayers," he said.

Click here to read McCain's full remarks at the hearing.

Click here to read Clinton's full remarks at the hearing.

Click here to read Obama's full remarks at the hearing.  

FOX News' Jennifer Griffin and Trish Turner contributed to this report.