WASHINGTON - Democrat Joe Sestak raised about $312,000 in the first three months of 2015 for his Senate campaign, barely one-tenth of the amount raised by the Republican incumbent he hopes to unseat, Sen. Pat Toomey.

Campaign finance records show Sestak had $1.7 million on hand through March, a month during which he spent most of his time on a largely solitary 422-mile hike across Pennsylvania. A campaign spokeswoman said the figures were "where we want to be."

But the totals suggest Toomey running away, at least in the money race: The Republican raised more than $2 million in the first quarter and had $7.2 million by the end of March.

The figures mean Sestak hasn't built the kind of money lead that might scare off potential Democratic rivals or calm worries within his party about his candidacy in a race deemed critical to Democratic hopes of retaking the Senate.

"It's tough for the admiral to raise the kind of money he wants to raise in state when there are national party officials who are looking for other candidates," said Scott Freda, a former deputy finance director for the Democrats' national Senate campaign arm.

Freda said Sestak would have to rely on the grassroots donors who have backed him before "to show there's momentum and that his core group is following him."

He also predicted that Toomey could have more than $10 million by the time a Democratic primary ends, while Sestak may have to fight just to win the nomination. Last week, Allentown Mayor Ed Pawlowski became the second Democrat in the race, and others may follow.

Another Democratic operative with experience in the state - who asked not to be identified critiquing Sestak's fund-raising - said a more encouraging quarterly sum for a Senate candidate at this point would be $500,000 to $700,000.

In 2009, when Sestak geared up for his first Senate bid, he raised $550,000 in the first quarter. (He was also a sitting congressman at the time.)

Toomey, meanwhile, has had help from Democrats.

David L. Cohen, who was chief of staff to Mayor Ed Rendell and is now a top Comcast executive, hosted a Toomey fund-raiser Monday at the cable company's Philadelphia headquarters. It is at least the second time Cohen has helped Toomey raise money.

Toomey campaign manager Peter Towey said the senator received support from several prominent Democrats.

"They're not looking at one issue," Towey said. "They're looking at [Toomey's] body of work."

jtamari@phillynews.com

@JonathanTamari