Congressional Democratic candidate John Foust speaks to constituent Regina Myers at Joe's Pizzeria in Sterling on April 15. (Melina Mara/The Washington Post)

Democrats are using a strong fundraising quarter for Fairfax County Supervisor John W. Foust to argue that the hotly contested race to replace retiring U.S. Rep. Frank R. Wolf (R-Va.) is tilting in their favor.

After collecting $705,000 since April 1, Foust’s campaign has twice as much cash available as his Republican opponent, Del. Barbara J. Comstock (Fairfax).

Federal disclosure reports filed this week show Foust’s campaign has $1.1 million on hand, compared with Comstock’s $576,000. Foust’s total includes $400,000 that he has lent his campaign, including $150,000 in the most recent quarter.

Comstock, a protege of Wolf’s whose extensive Republican Party connections made her a favorite to win one of the country’s most closely watched congressional races, has raised $611,000 since April 7, her disclosure report shows.

Though fundraising numbers offer only a glimpse of the support a candidate will receive from voters during the November election, the money pays for ads and other marketing materials that can affect public opinion.

For that reason, the Foust campaign is treating the numbers like a victory and saying they indicate momentum is on the side of the Democrat, who represents the Dranesville district on the county board.

“We did it!” Foust’s campaign boasted in a blast e-mail to supporters. “We TROUNCED Barbara Comstock’s fundraising numbers.” The e-mail also gave the impression that it was showing the number of online donations climbing rapidly, in real time. But each time it was opened, the e-mail started with the same number of supporters: 2,264.

Republicans played down the significance of the fundraising numbers. The lower amount of cash Comstock has available reflects the fact that she recently emerged from a primary election, where her campaign was forced to buy ads to respond to attacks from her GOP rivals, they said. Foust was selected as the Democratic nominee without opposition.

Comstock’s supporters also noted that Foust’s $400,000 in personal loans diminishes the significance of his fundraising total.

“Barbara Comstock just won her primary and still had an incredible fundraising quarter while John Foust has had to loan his own campaign hundreds of thousands to stay in the game,” said Katie Prill, a spokeswoman for the National Republican Congressional Committee.

Foust supporters noted that his campaign has more donations under $200, which they said is a sign of who is waging a better grass-roots effort. Foust has collected nearly $84,000 in such donations since early April; Comstock gathered $51,591, reports show.

“Many of the initial characterizations of Comstock’s ability to dominate every race she’s in were exaggerated,” said Shaun Daniels, Foust’s campaign manager. “John Foust’s numbers, particularly the fact that he has raised more from smaller donors, show the level of excitement in the district, in the party and in the state that is unmatched by Comstock.”

But the fundraising race is far from over, and both sides are pledging to intensify their efforts before the November election in what promises to be among the nation’s most expensive congressional elections.

For example, the National Republican Congressional Committee has already reserved $2.8 million in television time dedicated to Comstock’s efforts, Prill said.