In the civil war of the Democratic nominating season, Tuesday night’s Potomac Primary was Gettysburg.

That’s the argument Barack Obama’s campaign was making Wednesday, saying the Illinois senator’s three-contest sweep of the Virginia, Maryland and Washington D.C. primaries marked a “decisive” turning point in his battle with Hillary Clinton.

Obama campaign manager David Plouffe said on a conference call that it is now “next to impossible” for Clinton to close Obama’s lead in pledged delegates.

“We couldn’t be in a stronger position right now, and the last really five days, we believe, will be looked back at as a very decisive period in the nomination contest,” Plouffe said. “We think it really put us on the path to the nomination.”

Obama has won seven straight contests since Saturday, not counting the Virgin Islands, and on Tuesday he took the lead in overall delegates for the first time since the primary and caucus season began last month.

The latest Associated Press tallies show Obama with 1,223 delegates and Clinton with 1,198. It takes 2,025 to seal the nomination.

The difference appears negligible, but Clinton has found herself on the defensive.

The New York senator is staking her campaign on big wins in Ohio and Texas, which hold their primaries on March 4, along with two other states.

Chief strategist Mark Penn released a “path to the nomination” memo Wednesday outlining how, by competing for the nearly 500 delegates at stake in Ohio, Texas and Pennsylvania, which votes a month later, the campaign can close the slim delegate gap. Penn said the number of delegates matters — not the numbers of states won or perceived “momentum.”

After being shut out over the weekend, Clinton replaced her campaign manager Patti Solis Doyle, and her deputy campaign manager left shortly after. Looking to shake things up, Clinton seemed more aggressive in McAllen, Texas, Wednesday, going after Obama for lacking concrete plans to address the housing crisis and provide universal health care.

“I am in the solutions business. My opponent is in the promises business,” Clinton said. “Our economy is losing jobs. The housing crisis is spreading. I have solutions to these economic challenges. The question today is, does Senator Obama? …We need real results, not more rhetoric.”

John McCain, the GOP front-runner, has also accused Obama of lacking specifics.

Clinton later denied that her campaign is in turmoil, saying, “This is a long journey to the nomination. You know, some weeks … one of us is up, the other one is down. Then we reverse it.”

The campaign announced it would be holding large rallies in Texas next week, shooting for crowds of 20,000. It also aired a new ad in Wisconsin challenging Obama to debate in the state.

Clinton has declared herself the “underdog candidate” in next Tuesday’s Wisconsin primary; Obama’s native state, Hawaii, holds its primary on that day, as well.

Obama stands to have won every Democratic contest since Super Tuesday when March 4 comes around, making Ohio and Texas that much more important to Clinton.

Clinton held a boisterous rally in El Paso, Texas, Tuesday, making a strong pitch to a crowd of Hispanic voters, one of the groups Clinton hopes to tap into again to beat Obama. Hispanic voters were instrumental in her wins in California and Nevada.

But exit polls from Tuesday showed Obama eating into Clinton’s traditionally loyal bases of women, senior, Hispanic and white voters.

Plouffe said Clinton would have to win Ohio and Texas by a “blowout” in order for her to recover the lead in pledged delegates. He estimated Obama has a 136-delegate lead in pledged delegates.

Superdelegates — elected officials and party leaders who go to the August convention uncommitted to either candidate — have largely favored Clinton. But Plouffe argued that if the campaign can retain a lead in pledged delegates, the superdelegates will “ratify that outcome.”

Superdelegates make up about 20 percent of the total convention delegates, and are included in the AP tallies.

Obama, already claiming that he is the candidate of a “new American majority,” is focusing more and more on McCain, the likely Republican candidate, as he continues to rack up big victories over Clinton.

He also is crafting a message that is aimed at skimming another group Clinton is counting on in the Midwest: blue-collar, middle-class workers.

On Wednesday Obama delivered remarks — billed by his campaign as a “major economics address” — to a crowd at a General Motors factory in Wisconsin one day after the company released its worst financial losses ever.

He said as president he would spend $210 billion to create jobs in construction and environmental industries, carving out $150 billion to create 5 million so-called “green collar” jobs to develop more environmentally friendly energy sources.

“This agenda is paid for,” Obama said as the Republican National Committee promoted an “Obama Spend-O-Meter” online to track his proposals and portray him as a tax-and-spend liberal.

Obama explained that the money for his spending proposals will come from ending the Iraq war, cutting tax breaks for corporations, taxing carbon pollution and raising taxes on high income earners.

FOX News’ Aaron Bruns and Bonney Kapp and The Associated Press contributed to this report.