Tough confirmation hearings ahead as Obama begins second term President Obama officially submitted his initial round of Cabinet nominations to the Senate Monday, moments after wrapping up his inaugural address -- touching off what is likely to be the first battle of his second term. Top Republican lawmakers have already voiced opposition to three of the president's nominees -- for secretaries of Defense and Treasury, as well as director of the Central Intelligence Agency - though it's uncertain whether such resistance will be enough to prevent their confirmation. Among the contentious hearings expected is that of Jacob "Jack" Lew, current White House Chief of Staff and Obama's choice to replace Timothy Geithner as the next Treasury secretary. In his formal endorsement of Lew for the post, Obama said he "cannot think of a better person" to continue Geithner's work, and touted Lew as someone who has "built a reputation as a master of policy" and can "work with members of both parties and forge principled compromises." I trust his judgment, I value his friendship. I know very few people with greater integrity," Obama said of his former budget director, who also presided over "three budget surpluses in a row" while in the Clinton-era budget office. Lew's nomination, however, sparked early criticism from Republicans, most notably Alabama Sen. Jeff Sessions, ranking Republican on the Senate Budget Committee, who said, "Jack Lew must never be secretary of Treasury." Sessions cited what he called "outrageous and false" comments made by Lew during a bitter Senate hearing in February 2011, when Lew was serving as director of the Office of Management and Budget. During the hearing, Lew attempted to defend statements he and Obama had made claiming their budget blueprint would get the country to a point where "we're not adding to the debt anymore." Those statements, though, conflicted with projections showing the debt continuing to grow well into the future -- Lew argued the administration was merely referring to "primary balance," or federal spending that does not count interest payments. A date for Lew's confirmation hearing has not been set. Another nominee expected to draw opposition is former Sen. Chuck Hagel, a Nebraska Republican and Vietnam War veteran Obama has tapped to become the next Defense secretary. Hagel, if confirmed, would replace current Defense chief Leon Panetta and be one of the few Republicans to serve in Obama's Cabinet. But some are questioning Hagel's commitment to Israel's national security, as well as his toughness on Iran. Sen. Pat Roberts, R-Kan., and Sen. John Cornyn, R-Texas, are among a handful of Republicans who have already said they will oppose the former two-term senator's confirmation. The Senate Armed Services Committee is expected to begin Hagel's confirmation hearing on Jan. 31. John Brennan, Obama's pick for CIA director, has also sparked opposition, with some lawmakers questioning potential ties to controversial interrogation tactics used by the CIA during the George W. Bush administration. Brennan, who currently serves as chief counterterrorism adviser, has denied supporting such harsh interrogation practices. "While Mr. Brennan's resume is commendable, I have questions about how he would lead the CIA and what changes he would embrace in light of the committee's problematic findings about the agency's detention and interrogation program," Sen. Mark Udall, D-Colo., a member of the Senate intelligence committee, reportedly said. Although I cannot disclose those classified findings, I am troubled by them. Sen. Lindsey Graham, R-S.C., said Brennan, who currently serves as chief counterterrorism adviser, should not be confirmed until the administration answers more questions about the conflicting information that emerged in the September attack on the U.S. Consulate in Benghazi. His hearing before the Senate Select Intelligence Committee is slated for Feb. 7. Sen. John Kerry, D-Mass., has been nominated to replace Secretary of State Hillary Clinton, and political observers say his confirmation hearing, to begin Thursday, is not expected to be widely contested. Other vacancies that the president must fill include Labor secretary.