President Bush’s plans to give a recess appointment to his choice for the No. 2 spot at the Social Security Administration could derail any chance of a Social Security overhaul, a top Senate Democrat said Wednesday.

Bush announced that he would name Andrew Biggs to the position of deputy commissioner, bypassing Senate confirmation.

Biggs is a supporter of Bush’s comatose plan to create individual investment accounts in Social Security, a proposal rejected by virtually every elected Democrat and a sizable minority of Republicans.

Some lawmakers, though, are still considering other changes to address Social Security’s long-term fiscal problems. One of them, Senate Finance Chairman Max Baucus, D-Mont., said the appointment of Biggs dimmed any chance for success on that front.

“Prospects for getting real Social Security reform anytime soon just took a big hit with this recess appointment,” Baucus said in a statement.

Biggs is now associate commissioner of the SSA’s Office of Retirement Policy. Before joining the administration, he was deputy director of the libertarian Cato Institute’s Project on Social Security Privatization — now called the Project on Social Security Choice. The Cato Institute is a strong advocate for replacing some or all of Social Security’s guaranteed retirement benefit with individual investment accounts.

In 2005, Bush pressed Congress to overhaul Social Security with individual accounts. The idea was blocked by congressional Democrats, who were nearly unanimously opposed to individual accounts. Most Democrats believe the accounts would be too risky for retirees and would cost too much to establish — trillions of dollars over decades, according to the Congressional Budget Office and other analysts.

Biggs was originally nominated last November. Baucus, said in February that he would not hold a hearing on the nomination because Biggs’ history as an advocate for individual accounts left him unqualified for the position. Individual accounts, Baucus said in his statement Wednesday, are a “settled debate” that Biggs’ appointment would re-open.

The White House criticized Baucus for the decision at the time, and warned that Bush would not withdraw Biggs’ nomination, foreshadowing his recess appointment.

“This administration is clearly not serious about leaving behind the failed schemes of the past and moving on to constructive discussions about the future of Social Security,” Baucus said.

Had Biggs been confirmed by the Senate, he could have served a six-year term as deputy SSA commissioner. As a recess appointment, he can still serve almost two years, until the end of the 110th Congress — almost the entire remainder of the Bush presidency.