The decision has apparently been made. President Obama will not back down and is set to move forward with the nomination of former Sen. Chuck Hagel, a Republican who went against his party on the Iraq war, to succeed Defense Secretary Leon Panetta, reports Politico’s Mike Allen and Darren Samuelsohn. The announcement is expected Monday in what will likely be the president’s first public appearance since returning to the White House from vacation Sunday. Reuters has confirmed the news, citing a Democratic aide, who also agrees the announcement could come as early as Monday.

Hagel’s nomination is likely to set off a fierce confirmation battle. It isn’t just Republicans who have voiced opposition to Hagel, but also pro-Israel and gay-rights groups, potentially hurting his prospects in the Democratic-controlled Senate. “I don’t think Dems just fall in line,” a Senate Democratic official tells Politico. “Ultimately, he may be confirmed. But at this stage, his fate is totally up in the air. He will really have to work hard to overcome some of his previous statements and positions.” McClatchy pointed out Friday that while Obama has generally avoided controversial selections for major posts, choosing another candidate would have also been damaging for the president, “because it would have been his second surrender on a top Cabinet choice within a month.”

Susan Rice withdrew her name from consideration as a possible secretary of State nominee last month following a wave of criticism from Republicans over the Benghazi attacks.

Hagel’s confirmation battle is likely to center around what the Weekly Standard’s William Kristol has called Hagel’s “dangerous views on Iran and his unpleasant distaste for Israel and Jews.” In particular, critics have seized on 2008 comments Hagel made about how he sometimes opposes pro-Israel groups. But gay-rights groups have also opposed Hagel for disparaging an ambassadorial nominee as “openly, aggressively gay.” Hagel has apologized for the comment.

Senate Minority Leader Mitch McConnell refused to throw his support behind Hagel on Sunday, telling ABC that “I’m going to wait and see how the hearings go” to figure out whether the former senator’s views “make sense for that particular job.”