(CNN) - Two new polls suggest dead heats in the Senate battles in Colorado and Wisconsin, two states where Democrats are trying to hold onto seats.
A St. Norbert College Survey Center/Wisconsin Public Radio poll released Tuesday indicates that Republican nominee Ron Johnson holds a 49 to 47 percent advantage over Sen. Russ Feingold among likely voters. Johnson's two-point margin is well within the poll's sampling error.
Other recent polls indicated a larger single digit lead for the Republican challenger. According to a CNN/Time/Opinion Research Corporation poll released last Wednesday, the three-term Democratic senator trailed Johnson by eight points. A Reuters/Ipsos survey also released last week indicated Johnson, a businessman who enjoys the support of many in the Tea Party movement, held a seven-point advantage over Feingold.
According to the St. Norbert poll, 42 percent of people questioned say they approve of job President Barack Obama's doing in the White House, with 52 percent saying they disapprove.
In Colorado, a Reuters/Ipsos poll released Tuesday indicates Republican challenger Ken Buck has a 48 to 45 percent advantage over Sen. Michael Bennet, with 5 percent undecided. Buck's three-point margin is within the survey's sampling error. Most other recent polls indicated a slightly larger single digit advantage for the GOP nominee.
According to the Reuters/Ipsos poll, among the larger sampling of all registered voters, Bennet holds a six-point advantage.
Buck, the Weld County district attorney, was once a long shot in the battle for the GOP nomination, but thanks in part to support from some in the Tea Party movement, he defeated former Lt. Gov Jane Norton, who was recruited to run by national Republicans and was the early favorite in the race.
Bennet survived a spirited Democratic primary challenge from former Colorado House Speaker Andrew Romanoff. He was appointed early last year to replace Democratic Sen. Ken Salazar, who stepped down to serve as Interior Secretary in the Obama Administration.
The Reuters/Ipsos poll was conducted October 15-17, with 600 registered voters in Colorado, including 402 likely voters, questioned by telephone. The survey's sampling error is plus or minus 4 percentage points for registered voters and plus or minus 4.9 percentage points for likely voters.
The St. Norbert poll was conducted October 12-15, with 402 likely voters in Wisconsin questioned by telephone. The survey's sampling error for likely voters is plus or minus 5 percentage points.
–Follow Paul Steinhauser on Twitter: @psteinhausercnn