At least 70 House seats in play, says Obama's campaign adviser

President Obama's top political guru said Tuesday that he believes 70 House races and 15 Senate races are in play this fall.

White House senior adviser David Plouffe — Obama's 2008 presidential campaign manager — said that a bevy of races were in play, from the national to local level.

"There are a lot of competitive races out there. There's going to be at least 70 House races in play, about 15 competitive Senate races, a couple dozen tough gubernatorial races," he said in a video to supporters of Organizing for America, the president's political arm.

Plouffe painted a picture of a dire electoral landscape in which, if Democrats were to lose the majority of those races, their losses would be massive.

The Democratic political guru encouraged party members to get out the vote this fall by helping to volunteer, and focus in particular on turning out first-time voters who supported Obama in 2008.

"What we all do over the next 50-some days is going to make a difference, and turn races that we might lose 51-49 into wins by 51-49," he said.

Plouffe's push also comes as new surveys show Republicans well-positioned ahead of November's elections. The GOP maintains strong leads in key electoral indicators, leading some election-watching groups like the nonpartisan Cook Political Report to project that Republicans are within striking distance of winning back the House.

Republican leaders have been much more cautious in making specific predictions about how many seats they're poised to win this fall. House Minority Leader John Boehner (R-Ohio), who would become Speaker if the GOP wins back the House, has said that as many as 100 House seats are in play.