Girding for the campaign's homestretch, President Barack Obama is quietly using the powers of his office to fire up a reeling Democratic Party.

Though Obama is off the campaign trail for three full days this week, he's personally targeting key Democratic constituencies from the White House, holding conference calls with union activists and campaign volunteers, and doing interviews with radio stations that draw largely black audiences. Many of these campaign events for the midterm elections are not publicized by the White House.

On Wednesday, Obama will tape an appearance on "The Daily Show with Jon Stewart," an irreverent comedy show with a host who aims for younger audiences and has become a prominent voice in today's politics.

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The president will wrap up the week with a campaign swing through five states where Democratic candidates are locked in tight contests.

It's a homestretch strategy based on how the White House believes the president can be most effective in an election in which his name is not on the ballot but his agenda is up for debate. According to a recent Associated Press-GfK poll, nearly half of likely voters say their votes for the House are intended to send a message about Obama.

White House officials say that while they still see value in the large rallies Obama has been holding across the country this month — he'll headline three more this weekend — they also recognize that with just six days until the election, many voters have already made up their minds.

"You've identified who your voters are," White House spokesman Robert Gibbs said Tuesday, adding that now is the time to get those voters motivated to show up on Election Day.

Obama held a conference call with thousands of union activists Tuesday night to thank them for the hours they've spent knocking on doors and working phone banks to boost turnout for Democratic candidates.