Jack Lew nominated for US Treasury Secretary

President Barack Obama made it official Thursday, nominating White House chief of staff Jack Lew to replace outgoing Treasury Secretary Tim Geithner.

Obama called Geithner, who is due to leave by the end of January, one of "our finest Secretaries of the Treasury" and praised Lew for his budget-balancing abilities during the Clinton administration.

"These are two outstanding public servants," Obama said.

While calling it "bittersweet" to lose his chief of staff, the president joked he nearly rescinded Lew's nomination after learning of his now-famous indiscernable signature that's made the rounds in the press.

Lew later joked that he discovered yesterday that he and Geithner "share a common challenge with penmanship."

Before taking on the chief of staff job, Lew, 57, served as the White House budget director, was twice the director of the Office of Management and Budget, and also worked as an aide to late House Speaker Tip O’Neill.

As White House budget director, Lew clashed with Republicans during the debt ceiling fight in the summer of 2011, which may cause some GOP members of Congress to give him a hard time in his confirmation hearings, Fox News noted.

According to Bloomberg's Hans Nichols, "The next Treasury secretary will play a leading role in working with Congress to raise the government’s $16.4 trillion debt ceiling."

Candidates to take over Lew’s White House chief of staff job include Dennis McDonough, a deputy national security adviser, and Ron Klain, who has served as Vice President Joe Biden’s chief of staff, according to Bloomberg.