WILMINGTON, Del. — Christine O’Donnell’s GOP Senate campaign is buying three 30-minute television ads for the final stretch, she announced Sunday at a Tea Party Express rally, where she insisted that the race is closer than it seems.

She has purchased the three ads, to air Sunday night and at 10 a.m. and 3 p.m. Monday, with the financial help of the tea party movement to showcase stories she hears on the campaign trail. “Tell everyone to tune in,” she said.

Such long TV segments won’t be cheap, but they could pack a punch for a campaign that has consistently lagged the Democratic candidate by double digits in the polls. Barack Obama successfully used the tactic to make his closing argument in his 2008 presidential campaign.

O’Donnell argued Sunday that she’s winning first-time voters who aren’t included in polls and that Democrats are worried, pointing to Vice President Joseph Biden’s scheduled appearance at a rally Monday for her Democratic rival, Chris Coons, as evidence.

“They wouldn’t spend the day before Election Day in Delaware if they didn’t know it was tight,” O’Donnell said as about 1,000 conservatives from Delaware, Maryland and Pennsylvania cheered along the Christina River waterfront.

O’Donnell accused the media of attacking conservative candidates and said liberals are afraid “something special” is happening in Delaware.

“We’re in it to win it,” she said, pointing out that political watchers underestimated her before she walloped Rep. Mike Castle in the GOP Senate primary last month. But Coons is favored to win Tuesday’s election, thanks to a more moderate general electorate than the Republican primary voters and some of O’Donnell’s stumbles along the way.

In a testament to the race’s national stakes, Senate Majority Leader Harry Reid’s name was mentioned as often as O’Donnell’s during Sunday’s rally, the 28th stop on a bus tour that began in Reno, Nev. The Tea Party Express showed a new attack ad against the Nevada Democrat, and organizers said he is their “No. 1 target.” The group asked the crowd to buy a $20 commemorative booklet to help fund ads supporting Reid’s opponent, Sharron Angle, and fellow GOP candidates Joe Miller in Alaska and Marco Rubio in Florida.

Rally attendees said they didn’t care that O’Donnell is highly unlikely to win, and many said they hoped the event would help boost turnout for GOP House candidate Glen Urquhart. “The first vote I will cast is to fire” Speaker Nancy Pelosi (D-Calif.), Urquhart said from the rally’s stage.

Brenda Brown, of Laurel, said the polls don’t discourage her. “I’m going to vote my conscience and my principles,” she said.

Organizers asked the crowd to knock on doors and volunteer at phone banks during the final 48 hours until the election, and they warned that Democrats “will lie, cheat, steal and do everything they can to win.”

“On Tuesday, we’re going to take out the trash,” Amy Kremer of the Tea Party Express said to applause.