Colorado Becomes New Battleground for Senate

With the U.S. Senate divided almost evenly along party lines, few contests this year are the focus of intense scrutiny. The latest has become the one in Colorado, after Republican Sen. Ben Nighthorse Campbell (search) announced last week that he plans to retire.

Since then, both parties have scrambled to find candidates who could win his seat in the fall. Currently, the Senate is 51-48-1, and Campbell's hold on the seat seemed a certainty to Republicans.

Now, Colorado joins eight other states as toss-ups in November.

When popular GOP Gov. Bill Owens (search) declined to run for Campbell's seat, the GOP started to worry.

"When he said no, that meant that you are now down into the second tier," said political analyst Floyd Cirruli.

The second tier also dropped out, leaving former Rep. Bob Schaffer (search) as the likely winner of the April 13 GOP primary.

Meanwhile state Attorney General Ken Salazar (search) announced his bid for the Democratic nomination, and many expect him to easily win the nomination next month, and be hard to beat in November.

Click here to watch a complete report by Fox News' Carol McKinley.