The poll, conducted by Democratic firm Public Policy Polling, gives Udall a 50 percent approval rating, with only about a third of voters disapproving of his job performance.
Though he's up for reelection in a swing state, no Republican challengers have yet emerged, and he leads every potential challenger.
But there's indication that Republicans could have a chance to make inroads, if a candidate emerges soon, as he pulls less than the 50 percent support considered comfortable for an incumbent against the strongest possible Republican challenger, former Rep. Bob Beauprez.
Udall takes 48 percent support to Beauprez's 41 percent support. But against the six other potential Republicans tested, Udall leads by anywhere from 10 to 13 percentage points.
The PPP survey was conducted among 500 Colorado voters from April 11-14, and has a margin of error of 4.4 percentage points.