Story highlights The ads come at an urgent time for Democrats

Polls are tightening in crucial battleground states

Washington (CNN) President Barack Obama and Michelle Obama have cut a series of radio ads targeting black voters, hoping to turn out the crucial bloc as their numbers have lagged in early voting.

The ads, which are being bankrolled by the House Democrats' political arm, are specifically aimed at seven congressional districts with major African American populations — two in Florida, two in Nevada, one in California, one in Kansas and another in Nebraska. The ads will run on at least two popular stations per district, including hip-hop and R&B stations, running at least twice an hour until Election Day, according to House Democrats.

And the President has this blunt message to black voters: "I need you."

"We have the opportunity to build on all the progress we've made, to fight for the issues you and I believe in," he says in one ad. "I'm doing everything I can to make sure our Democrats all around the country have what they need to win, and that's why I need you."

In a separate ad, the first lady says Democrats need black voters to "continue my husband's legacy, building on the progress we've made."

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