DENVER -- Denver Public Schools Superintendent Michael Bennet has been chosen to fill the U.S. Senate seat being vacated by Ken Salazar, numerous sources said Friday.

A member of Rep. Ed Perlmutter's staff confirmed to 7NEWS that the congressman has been told he was not selected.

A spokesman for Salazar would neither confirm nor deny the reports and directed inquiries to Gov. Bill Ritter's office.

Ritter is expected to make a formal announcement Saturday at 2 p.m.

Bennet had been mentioned as a possible choice for President-elect Barack Obama's education secretary, but Obama chose 44-year-old Arne Duncan, chief executive officer of Chicago public schools for the Cabinet post.

Bennet was considered a dark horse candidate for the Senate spot because of his lack of legislative experience. A message left for Bennet at his DPS office, which was closed for winter break, was not immediately returned.

"He's certainly qualified, but he wasn't on any of the public's short lists," said Seth Masket, an assistant professor of political science at the University of Denver. Masket said Bennet would have his work cut out for him as senator, primarily defining himself to voters across Colorado. “He'll probably be championing a number of issues beyond education in a way to make him more visible to the rest of the state," Masket told 7NEWS Friday. The Yale-educated lawyer in 2003 was tapped to be chief of staff for Denver Mayor John Hickenlooper, who then encouraged him to apply for the superintendent job for the 150-school city system two years later.

In June 2005, the Denver Board of Education unanimously appointed him superintendent of Denver Public Schools after he promised to provide each school with a highly skilled faculty and was able to get teachers to support merit pay. He also promised to track student progress and provide help.

The school board said Bennett delivered and students made strong improvements in reading, math, writing and science.

According to Denver Public Schools, the district posted a 6.2 percent increase in reading scores over the three years, more than four times the growth of the state. In math, there was a 6 percent gain, more than twice the growth of the state, and in the middle grades, Denver saw gains of 10 percent in reading and 9 percent in math.

Colorado Republican Party Chairman Dick Wadhams said the seat was already being targeted in 2010 by both parties, but he said the choice of Bennet was "perplexing."

"There are some admirable things Bennet did with Denver Public Schools, but he'll be judged by what he does in the Senate. There are major issues coming up this year, and he'll have to vote on tax increases and bailouts. Those votes will define Michael Bennet," Wadhams said.

Wadhams told 7NEWS he anticipated Hickenlooper would receive the nod for the seat.

Wadhams viewed Hickenlooper as a higher profile, harder-to-beat incumbent senator in the 2010 election.

"Take (Hickenlooper) out of the equation, and this Senate seat becomes much more competitive,” Wadham said.

Political consultant Floyd Ciruli said Bennett is a risky choice for Democrats, who will have to spend millions of dollars defending that seat in two years.

"He's the one candidate on the list who has the least political experience. I don't think anyone knows his views on anything except education. This is surprising," Ciruli said.

Among the other Democrats who competed for the vacancy were term-limited state House Speaker Andrew Romanoff and 7th District Congressman Ed Perlmutter. Hickenlooper also asked to be considered. A message left for Romanoff was not immediately returned.

Former Denver Mayor Federico Pena and Rep. Diana DeGette told Ritter they weren't interested in the job.

Salazar will stay in his seat until he's confirmed as Interior Secretary following Obama's inauguration, which could take several weeks.

The quiet Colorado Senate search was a marked departure from Senate searches in the two other states with Senate vacancies.

In Illinois, Democratic Gov. Rod Blagojevich faces federal charges of seeking bribes in exchange for his appointment to Obama's Senate seat. Blagojevich has insisted he did nothing wrong and named an Obama replacement Tuesday, state Attorney General Roland Burris.

In New York, where Sen. Hillary Clinton has been tapped as secretary of state, the high-profile search includes Caroline Kennedy.