The nasty fight long has been seen as a proxy for the never-ending scuffles between the Democratic president and congressional Republicans, with barely any reservoir of good will between the White House and lawmakers, and the GOP still smarting over the November election results.
Barring any surprises, the drawn-out battle over Hagel's nomination probably will end this coming week with his Senate confirmation. But his fellow Republicans have roughed him up.
A vote is expected on Tuesday.
In the weeks after Obama secured a second term, Republicans knocked out a presidential favorite, U.N. Ambassador Susan Rice, and dashed her secretary of state hopes over her widely debunked remarks about protests precipitating the assault on the U.S. diplomatic mission in Libya on Sept. 11.
Emboldened Republicans then set their sights on Hagel, whose GOP classification won him no points with the party.
The former two-term Nebraska senator was widely viewed as a political heretic. He disagreed with President George W. Bush over the Iraq war, stayed on the sidelines in the 2008 president race between Obama and the Republican nominee, Arizona Sen. John McCain, and endorsed fellow Vietnam veteran and former Democratic Sen. Bob Kerrey in last year's Nebraska Senate race.
Republicans remember it well.
"There's a lot of ill will toward Sen. Hagel because when he was a Republican, he attacked President Bush mercilessly, at one point said he was the worst president since Herbert Hoover, said the surge (of U.S. troops in Iraq) was the worst blunder since the Vietnam War, which is nonsense, and was anti-his own party and people," McCain said in an interview on Fox News on the day Republicans stalled Hagel's nomination.
Hagel didn't help his cause with his past opposition to unilateral penalties against Iran, his comment about the influence of the "Jewish lobby" in Washington, his support for reducing the nation's nuclear arsenal and remarks that created widespread doubts about his backing for Israel.
His halting and uneven performance at his confirmation hearing also hurt his nomination.
McCain, one of Hagel's friends during their years in the Senate, would have been a crucial vote to help sway other Republicans to back the nominee. Instead, he is one of more than a dozen opposing Hagel.
"I think he will have been weakened, but having said that, the job that he has is too important," McCain told reporters Friday during a visit to Mexico. "I know that I and my other colleagues, if he's confirmed, and he very likely will be, will do everything we can to work with him."
The nomination fight also is about the business of re-electing Republicans in 2014. Challenging the Democratic president over his nominations and policies is clearly a winner with the conservative base, a point not lost on GOP incumbents wary of challenges from the tea party.
South Carolina Republican Sen. Lindsey Graham, who's up for re-election next year, is getting high marks from Republicans for his relentless effort to get more information about the Sept. 11 attack in Benghazi, Libya, and his fierce opposition to Hagel.
"Most people down here think he's dead-on in his arguments and hope that he continues to press the issues," said Warren Tompkins, a longtime GOP strategist.
The Libya attack that killed Ambassador Chris Stevens and three other Americans has been a political flashpoint for Republicans who accused the Obama administration of an election-year cover-up of a terrorist assault.
An independent review conducted by respected former diplomats failed to mollify the GOP, who demanded testimony from Hillary Rodham Clinton, secretary of state when the attack occurred, and Defense Secretary Leon Panetta.
Graham has been at the forefront in seeking emails, communiques and videos while threatening to delay both Hagel's nomination and that of CIA Director-nominee John Brennan, who also has become entangled in the Libya dispute.
During a stop in Easley, S.C., this past week, Graham insisted that his effort has nothing to do with politics.
"It's not because he's a Democrat and I'm a Republican," he said, referring to Obama. "It's because it really was system failure and we need learn from it. We have not gotten the information, and we're going to get it if I have to die trying."
The White House has agreed to give the Senate Intelligence Committee additional documents related to the Benghazi attack, according to a congressional aide said. The material includes emails between national security officials showing the debate within the administration over how to describe the attack.
Graham also has been intense in opposing Hagel, portraying the former GOP senator as an out-of-the-mainstream radical. Some of the toughest questions of Hagel during his confirmation hearing last month came from Graham, who seized on Hagel's "Jewish lobby" remark and asked him to "name one dumb thing we've been goaded into doing due to pressure by the Israeli, Jewish lobby."
Hagel was often tentative in his response in the face of GOP grilling.
"He's leading, he's governing," Glenn McCall, the chairman of the York (S.C.) County Republican Party and a GOP committeeman, said of Graham. "More and more I talk to Republicans -- and even those that are conservative Democrats -- I think folks are looking for leadership."
Both Tompkins and McCall cited a Winthrop University poll released last week that showed Graham with strong support from registered Republicans in the state, with 72 percent holding a favorable opinion of the senator.
It's a turnaround from several years ago when Graham's work with Democrats on climate change and immigration as well as his votes for Obama's nominees for the Supreme Court angered South Carolina Republicans, with some calling him out of touch and Charleston and Lexington counties voting to censure him over his bipartisan work.
"It might be the right thing to do ... but when you partner with Hillary Clinton or you partner with John Kerry, you're going to be looked upon with a lot of suspicion in South Carolina," Tompkins said. "You have to be careful who you dance with."
Kerry, a former Democratic senator from Massachusetts, has just replaced Clinton as secretary of state.
Graham still may face a primary challenge, but he and other GOP incumbents are determined to head off any conservative uprising as Utah Sen. Orrin Hatch successfully did in his 2012 race. They want to avoid the fate of the only GOP primary loser last year -- Indiana's longtime Sen. Dick Lugar.
Texas Sen. John Cornyn, the No. 2 Republican and a candidate next year, took the lead on the Senate floor to block a vote on Hagel on Feb. 14 and was one of 15 Republicans last week to call for Obama to withdraw the nomination.
Cornyn got a primary challenger last week.