WASHINGTON – A political enthusiasm gap is helping Republicans in their effort to roll up big gains in the congressional elections. GOP supporters are a lot more interested in getting their party’s candidates elected than Democrats are in electing theirs, a new AP-GfK poll shows.

Democrats struggling to defend their control of Congress have lucked out in one way: Republicans are at least as unpopular as they are, the poll shows. Yet GOP voters are more fired up, leaving the Democrats little more than a month to energize their supporters.

How? They’re using President Obama and his Cabinet. Al Gore, too. And until Election Day dawns on Nov. 2, the Democrats will try to refocus voters from their anger over the stubbornly limp economy to the risks of putting Republicans in charge on Capitol Hill.

It’s a common theme: A TV ad by Senate Majority Leader Harry Reid, D-Nev., accuses his GOP opponent of a proposal that is “not just extreme, that’s dangerous,” while one by Rep. Larry Kissell, D-N.C., says his challenger would shield tax breaks for companies that ship American jobs overseas.

“There’s a level of frustration the American people have that we understand and that obviously Democrats are trying to address,” said party spokesman Brad Woodhouse.

“But I haven’t run into anybody who says they want to go back to the fall of 2008,” he said, when Republicans held the White House.

Also helping Democrats round up votes will be their traditional labor union allies, who plan to spend nearly $100 million helping the party’s candidates. This includes plans by the AFL-CIO, the nation’s largest labor federation, to mobilize members in 26 states and target 70 House races and 18 Senate contests with television ads, phone banks and leaflets.

Republicans, energized by tea party fervor and capitalizing on frustration over the sluggish economy, are tailoring their campaign strategy to reflect concerns about job losses and government growth under Obama as he fought a recession and won a battle to revamp the country’s health care system.

In a fundraising appeal e-mailed Friday, the head of the House Republican campaign arm, Rep. Pete Sessions of Texas, warned that the Democratic agenda means “America gets less — fewer jobs. Lower incomes. Less freedom.”

Says Rob Jesmer, executive director of Senate Republicans’ campaign committee: “We need to continue to tell people that the more Republicans who get elected, the less chance the president will have to enact his agenda.”

The Associated Press-GfK Poll this month shows that the public is fed up with both parties. Only 38 percent approve of how congressional Democrats are handling their jobs, and just 31 percent like how Republicans are doing theirs. Fifty-nine percent are unhappy with how Democrats are nursing the economy, 64 percent are upset by the GOP’s work on the country’s top issue.

More than half have negative views of each party. Most say Obama isn’t cooperating enough on the economy, but even more accuse Republicans of the same thing. And former President George W. Bush and former Alaska Gov. Sarah Palin — the only two Republicans the AP-GfK Poll tested — are significantly less popular than Obama.

Even so, Republicans have the upper hand because their supporters seem significantly likelier to show up on Election Day and vote.

In the AP-GfK Poll, 54 percent who strongly dislike Democrats express intense interest in the election, compared with just 40 percent of those with very negative views of Republicans. Nearly six in 10 who say their November vote will signal opposition to Obama also say they are extremely interested in the campaign, compared with only about four in 10 who say their vote will show support for him.

Overall, 49 percent of those supporting their Republican congressional candidate are very interested in the election, compared with 39 percent of those backing the Democrat in their local race.

The bottom line: Registered voters in the AP-GfK Poll are divided evenly over which party’s congressional candidate they will support, but Republicans have a slight edge among voters considered likeliest to show up.

Having even a scant edge in motivated supporters can make a big difference — especially in midterm elections, when only about 40 percent of voters nationally have been bothering to cast ballots, a figure than can dip to 30 percent in some states.

Aware of that, Obama will hit the road in the coming days, headlining at least four major rallies in Wisconsin, Pennsylvania, Ohio and Nevada.

During next week’s rally in Madison, Wis., Vice President Joe Biden and members of the Cabinet will fan out to college campuses across the country in hopes of activating students who heavily supported Obama in his 2008 election victory.

On Friday, former Vice President Al Gore joined the Democratic campaign to drum up party voters. He signed a fundraising e-mail for House Democrats saying Republicans’ goal is “to restore the very same policies followed for eight years by the Bush-Cheney White House.”