NEW YORK — President Barack Obama finally set the rumors to rest this week by formally nominating former Republican senator Chuck Hagel as the next secretary of defense.

When news of Hagel’s likely nomination surfaced in mid-December, it garnered stiff opposition from many quarters, but also vigorous support from a string of national security analysts and former officials and, more recently, from sources close to the administration.

Many Washington observers expected the formal nomination to be the end of the fight, as presidential nominations are almost always confirmed by the Senate. Any effort at torpedoing the nomination, many believed, had to focus on changing Obama’s mind before the nomination was formally announced.

But in the days that followed the Monday nomination, opposition from some quarters has only grown fiercer and better organized. Since the nomination, too, Hagel has had the opportunity for the first time to respond to the criticism himself.

On the right, many Republican groups, not to mention senators, are angered by Hagel’s vociferous criticism of Bush administration policies during his time in the Senate and more recent calls to cut the defense budget. And he didn’t make any Republican friends by endorsing Democrats Joe Sestak and Bob Kerrey in Senate races in 2010 and 2012.

Republican Senator Pat Roberts of Kansas was the latest to announce his opposition to the Hagel nomination, saying Tuesday that his foreign policy views and Hagel’s diverged too greatly. Roberts added his name to a growing – though still too short to matter – list of senators expressing reservations or outright opposition to Hagel’s appointment, including John Cornyn (TX), Marco Rubio (FL), Rob Portman (OH), John McCain (AZ), Lindsey Graham (SC), Kelly Ayotte (NH), Tom Coburn (OK) and Tom Cotton (AK).

The largest Christian Zionist group in the United States, Christians United for Israel, responded to the nomination with a statement that noted Hagel’s “past service to our country,” but insisted “his record concerning Iran and Hezbollah indicates an unacceptable blindness to the greatest security threat of our day.”

The Emergency Committee for Israel responded to the announcement by launching, on the very same day, the website chuckhagel.com, with an Internet address guaranteed to place the site near the top of any search for the nominee. The site argues against Hagel’s nomination, calling it “not a responsible option.”

But opposition was not limited to the right, or to foreign policy.

On Tuesday the website Buzzfeed reported on Hagel’s past opposition to “abortion in cases of rape and incest because those cases are ‘rare.’”

“I am pro-life with one exception — the life of the mother,” Hagel explained in campaign literature for his 1996 Senate campaign, according to the Omaha World Herald. “I oppose taxpayer funded abortions. We must promote adoption and support the strengthening of American families. I will vote with and support the pro-life movement,” he said.

This opposition to abortion even in cases of rape and incest may be relevant to the job of defense secretary, MSNBC’s Rachel Maddow noted. The Pentagon only recently added insurance coverage for abortions resulting from sexual assault to the insurance plans offered to US servicewomen.

Similar questions have been raised about gay rights in a Hagel Pentagon. Hagel will be the first defense secretary after the abolition of “Don’t ask, don’t tell,” a policy that forbade homosexual relationship within the US military and thus disqualified homosexual couples from the benefits available to military families. That policy change, too, will be tested under the next defense secretary, who will have a great deal of power in deciding the extent to which benefits will be expanded for gay families.

Gay rights groups are worried that some of Hagel’s past comments disparaging gays will be reflected in the new policies. (Hagel has apologized for at least one past statement, and Obama has said that “anybody who serves in my administration understands my attitude and position on [gay rights] issues.”)

In the end, Hagel will have the chance to defend his past statements before the Senate and explain his views on the future direction of the US military on a myriad of issues.

“I fully recognize that confirmation is up to the Senate,” he told the Lincoln Journal-Star the day he was nominated. “All I ask is a fair hearing, and I will get that. I am very much looking forward to having a full, open, transparent hearing about my qualifications and my record. All I look for is an opportunity to respond.”