DENVER -- Both vice presidential candidates will visit Colorado next week in an effort rally support for their campaigns as early voting begins in Colorado.

It is estimated that 60 to 70 percent of Colorado voters will vote by mail or early voting. Republicans and Democrats alike are gearing up for the home stretch.

"Lots of phone calls, lots of mail, campaigns running a lot of television ads right now because you have to do that earlier than normal," said Colorado Republican State Chairman Dick Wadhams.

At Obama's Colorado campaign headquarters volunteers were working the phone banks. "There is such a good energy. People are on the phone and stuffing envelops," said Tracy Shapiro.

Democratic vice presidential candidate Joe Biden will campaign in Greeley and Commerce City on Tuesday and in Pueblo and the Colorado Springs area on Wednesday.

Democrats said last week that Biden was coming to Colorado, but the specific sites weren't announced until Sunday.

Biden will appear at the University of Northern Colorado in Greeley in the Butler-Hancock Hally Gymnasium. Doors open at 10:30 a.m. The event is free to the public, but RSVP is encouraged. To RSVP, go to co.barackobama.com.

At 2:30 p.m. he will visit Adams City High School in Commerce City. The campaign said free tickets are required and can be picked up beginning at 5 p.m. Sunday at the campaign offices in Thornton at 550 Thornton Parkway, Suite 114 or in Commerce City at 6145 E. 72nd St.

For information, call 303-450-0167

Locations for the Pueblo and Colorado Springs visits haven't been announced.

This is Biden's first strip to Colorado since the Democratic convention in August. Palin campaigned in the Denver suburb of Englewood about two weeks ago.

Palin To Visit 3 Cities On Monday

Republican vice presidential candidate Sarah Palin plans campaign stops in Colorado Springs, Loveland and Grand Junction on Monday.

Palin, the governor of Alaska, has campaigned frequently in Colorado, whose nine electoral votes could tip a close election. She visited the Denver suburb of Englewood on Oct. 4.

Her first stop Monday will be in Colorado Springs for a rally at Security Service Field, home of the Colorado Springs Sky Sox, a minor-league affiliate of the Colorado Rockies.

She's scheduled to appear at noon at the Budweiser Events Center at the Larimer County Fairgrounds in Loveland.

Palin will then fly to Grand Junction to appear at Suplizio Field baseball stadium.

Her Colorado visit comes two days after she appeared on NBC's "Saturday Night Live" and boosted the show to its highest ratings in 14 years, according to early estimates.

Story: Palin Dishes Back On 'SNL'