Both parties sizing up Tea Party challenge

LESTER HOLT, anchor: Just over six weeks now until the midterm elections, and both parties find themselves dealing with the sudden impact of the tea party movement, including last week's victory in the Delaware primary by Republican Senate candidate Christine O'Donnell . NBC 's Mike Viqueira is at the White House tonight with more on this season of political upheaval. Mike , good evening.

MIKE VIQUEIRA reporting: Good evening, Lester . With Democrats facing big losses this fall, President Obama has issued a full-throated plea to the party's grass roots to get involved in the fall campaign. This as a new controversy involving a Republican candidate threatens to widen rifts within the GOP . The first family today, leaving the White House and walking to church on a quiet Sunday morning. It was a brief moment of calm in what has become a desperate campaign season for Democrats .

President BARACK OBAMA: I need you because this isn't going to be easy.

VIQUEIRA: Fearing a lack of enthusiasm as the election draws near and with Democratic control of Congress in doubt, last night the president delivered an urgent appeal to his party's base.

Pres. OBAMA: I need everybody to go back to your neighborhoods, to go back to your workplaces, to go to churches and go to the barber shops and go to the beauty shops and tell them we've got more work to do.

VIQUEIRA: Today Colin Powell , a Republican who bucked his party by backing Mr. Obama in 2008 , offered the president his advice on how to recover.

General COLIN POWELL (Former Secretary of State): Like a razor blade, just go right after the single issue that is uppermost in the minds of the American people , and that's employment.

VIQUEIRA: But there is trouble brewing for Republicans , as well.

Ms. CHRISTINE O'DONNELL: I dabbled into witchcraft, I never joined a coven.

VIQUEIRA: Delaware GOP Senate nominee Christine O'Donnell , known as a social conservative, seen in this 1999 television appearance with Bill Maher talking about her experiences with the occult.

Ms. O'DONNELL: (From ABC's " Politically Incorrect ," October 29, 1999 ): One of my first dates with a witch was on a satanic altar and I didn't know it and, I mean, there's a little blood there and stuff.

VIQUEIRA: Maher re-aired the footage Friday night. By this morning...

Mr. BOB SCHIEFFER: She said she had scheduling conflicts and couldn't be here.

VIQUEIRA: ... O'Donnell was a no-show for two national broadcast interviews. O'Donnell was backed by Sarah Palin and the tea party and defeated a more moderate Republican favored by GOP leaders in Washington . Today at least one who opposed O'Donnell has seen his fears confirmed.

Mr. KARL ROVE (Former Senior White House Adviser): There are serious questions that have been raised about Miss O'Donnell 's background character statements and previous actions.

VIQUEIRA: Democrats , meanwhile, hope the crack in GOP unity can give them a foothold for November.

Mr. TIM KAINE (Democratic National Committee Chairman): You know, the Republicans I think merged with the tea party , and in many instances they're finding out it's the Donner party .

VIQUEIRA: And, Lester , more on Christine O'Donnell . She was back in Delaware today campaigning. She tried to make light of those comments about her experience in witchcraft, telling an audience, 'How many of you didn't hang out with questionable folks in high school?' Lester :