TRENTON, N.J. » Faced with a widening political scandal that threatens to undermine his second term and a possible 2016 presidential run, New Jersey Gov. Chris Christie apologized again today, saying his administration "let down the people we are entrusted to serve" but that it doesn’t define his team or the state.

On the eve of his second term, the governor opened his annual State of the State address by touching only briefly on the issue before moving on to take credit for the state’s improving economy.

"The last week has certainly tested this administration," he told lawmakers and others gathered at the Statehouse. "Mistakes were clearly made. And as a result, we let down the people we are entrusted to serve. I know our citizens deserve better."

The scandal broke wide open last week with the release of documents showing the involvement of Christie aides and appointees in apparently politically orchestrated traffic lane closings in September that caused massive gridlock. He has fired one close aide and others on his team have resigned.

Christie first apologized last week during a nearly two-hour news conference, saying he was blindsided by his staff’s involvement. Christie has denied any knowledge in the planning or execution of the plot, and there is no evidence linking him to it.

A popular figure in the Republican Party, Christie won re-election by 22 points in November after earning high marks from New Jerseyans for his handling of the state’s recovery from Superstorm Sandy, and his stock had been rising as a potential candidate for president in 2016.

Now, he is hoping his State of the State address will help him rebound from the apparent political payback scheme that could damage his second term and cut short any ambitions to run for president.

In addition to discussing the economy, he was also to propose extending the public school calendar and lengthening the school day, though details will be left for another day, according to prepared remarks provided by the governor’s office.

Wendell Steinhauer, president of New Jersey’s largest and most powerful teachers union and a frequent adversary of Christie, said in a statement ahead of the speech that the group would welcome discussion of the proposal with Christie. But Steinhauer also criticized Christie for his veto Monday of a bill that would have implemented full-day kindergarten statewide.

An overhaul of public employee retirement benefits by Christie and the Legislature in 2011 was bitterly opposed by the union, which spent millions of dollars on anti-Christie ads during his gubernatorial campaigns.

The plan is the latest from a governor who has sought to retool schooling in grades kindergarten through 12 with mixed success.

He successfully overhauled century-old teacher tenure rules in a way the union supported, essentially eliminating lifetime job protections. But the Democrat-led Legislature has not gone along with his voucher plan, which would allow children in failing schools to attend classes elsewhere, including at private or parochial schools.

In his speech, Christie also is expected to revive the theme of bipartisanship, which has taken a hit as the political payback scheme has unraveled. While the governor has sought to package himself as someone willing to reach across the aisle to get things done, in contrast to politicians in Washington, the traffic plot exposed the petty partisan politics being practiced by some of his aides.

Two special legislative panels announced plans Monday to continue investigating, and federal prosecutors are also reviewing what happened.

Christie is set to be inaugurated for a second term Jan. 21.