Senate Republicans this week continued their challenge of the Obama administration by citing and exploiting vulnerabilities in several key nominees for the second term. The attacks created delays or expected close votes on three important nominees as Treasury and Defense secretaries, and as CIA director.

Update: A senate vote Feb. 14 failed to end a filibuster against the nomination of former Nebraska Sen. Chuck Hagel, right, to become Defense Secretary. Those cloture motion narrowly failed on the eve of incumbent Secretary Leon Panetta's resignation. The senate begins a 10-day recess Feb. 16. Hagel's nomination may still overcome opposition if he and the president stand firm. Rejection would be an unprecedented humiliation for Hagel and the president, and perhaps also embarrass Senate Majority Leader Harry Reid because he gutted filibuster reform last month after touting a deal with Republicans.

Another attack by Republicans centered on a $945,000 bonus that Treasury nominee Jack Lew, left, received following a brief stint of work for Citibank. Lew is White House chief of staff.

Separately, senate Democrats postponed for two weeks a confirmation vote for CIA nominee John Brennan following Republican demands that he provide more information about the administration's drone warfare program. Brennan is White House counter-terrorism chief after 25 years working at the CIA.

Republicans have voiced several complaints about their former colleague, Hagel, the first enlisted man wounded in combat ever nominated for the defense secretary post.

As part of the opposition to Hagel, South Carolina Sen. Lindsey Graham, for example, has demanded that the White House provide evidence of how President Obama spent his evening last fall on Sept. 11 after militants attacked a United States installation in Libya and killed four Americans.

The real reasons for opposition to Hagel appear to center on his reduced support for U.S. combat troops in Iraq before his retirement from the senate in 2009. The senate has scheduled a vote on the Hagel nomination for Feb. 15. The Armed Services Committee approved him this week 14-11 on a party-line vote, which one Republican missed. Neo-conservatives have furiously worked behind-the-scenes to thwart Hagel, in part by creating transparently phony side issues, such as criticism of an anti-gay comment Hagel made long ago.

Hagel's confirmation has become a memorable battle, in part because many of his opponents are strongly pro-war while always having avoided themselves the kind of sacrifice Hagel exhibited. Hagel, from modest means in Nebraska, was seriously wounded two times in Vietnam after enlisting with his brother, Thomas. They were not only a rare combination of siblings in the same combat unit, but they also saved each others' lives.