(CNN) - The crowded field of candidates who are challenging Democratic Sen. Michael Bennet of Colorado gets some new players this week.
Today, Republican former Lt. Gov. Jane Norton is expected to announce her bid with a three-city campaign swing through Denver, Colorado Springs and Grand Junction. Norton served as lieutenant governor under Republican Gov. Bill Owens from 2003 to 2007. She did not seek the top spot in the 2006 election, when Owens was term-limited, and is currently executive director of the Denver Police Foundation.
Norton joins at least five other Republican candidates who are considering a run for Colorado's GOP Senate nomination.
Tomorrow, Bennet gets another challenger - this time from his own party. Former Colorado House Speaker Andrew Romanoff is expected to officially announce his bid for the Democratic Senate nomination, with events planned in Pueblo, Colorado Springs and Denver.
Bennet was considered a surprise choice by Colorado Gov. Bill Ritter to replace Sen. Ken Salazar, who stepped down from his seat in January to serve as President Barack Obama's Interior Secretary. Bennet, who was superintendent of the Denver public school system, will have to defend the seat next year.