The first lady incorrectly identified Sen. Mark Udall (D) as "a fifth-generation Coloradan."
Democrats Sen. Mark Udall and House hopeful Andrew Romanoff feel the heat.
Dems worry the tactic won't be enough for Sen. Mark Udall (D) against Rep. Cory Gardner (R).
GOP-aligned Crossroads GPS released an ad hitting Sen. Udall for his support of ObamaCare.
A push to ban the drilling technique could hurt Sen. Mark Udall's (D) reelection chances.
Michelle Obama heads where her husband can't — Iowa, Colorado and Minnesota.
Democrat stood by his vote for ObamaCare while Gardner tacked to center on immigration.
Sen. Mark Udall (D-Colo.) hit for support of Obamacare and opposition to Keystone pipeline.
Here are five state issues that are playing big roles in the battle for the Senate.
President heralds vulnerable senator as "serious person who's trying to do the right thing."