Seeking to harness momentum from a House Democratic victory in the South Dakota special election last week, Minority Leader Nancy Pelosi (D-Calif.) has called a mandatory Member dinner to press for contributions and lay out her strongest case yet that the party can take back the House in November.

At the dinner, to be held on Capitol Hill Tuesday night, the Minority Leader will tell Members how the political landscape has improved in recent weeks, several key Democratic sources said. Pelosi will emphasize to Members that more districts are now winnable and urge them to step up their efforts from media outreach and local events to party contributions, the sources said.

Pelosi’s move comes just three weeks before the June 30 fundraising deadlines in which Democrats must make a strong financial showing.

“It is important Members understand our plan and how we can win,” said one Democratic leadership aide. “It’s also important for them to know that if we want to win, everyone has to participate.”

Pelosi usually makes a quarterly push to Members to pay their Democratic Congressional Campaign Committee dues at her weekly leadership lunches. But aides said the Minority Leader opted to host a special evening event to ensure higher attendance.

She told her Caucus last week they are all but required to be there. “You need a note from your doctor if you aren’t going to be there,” Pelosi privately told Members last week, according to one well-placed Democratic aide. “And not from your doctor, from my doctor.”

But one Democratic Member, speaking on the condition of anonymity, wasn’t inclined to show up if dues-paying is on the agenda.

“Now that I know what it’s about, I won’t be going,” the lawmaker said.

One senior Democratic aide suggested that Pelosi and other party leaders are turning up the heat because DCCC fundraising targets for Members haven’t been met this cycle.

The aide added that the South Dakota race won last week by Stephanie Herseth (D) cost the party $2.5 million — meaning that the DCCC must make up financial ground before races heat up in the fall.

“We haven’t met all our goals,” said the aide. “That’s why there is extra pressure to do this.”

Rep. Robert Matsui (D-Calif.), DCCC chairman, dismissed any suggestion that Members aren’t coming through but added that they could do more. He said this cycle — as is typical — Member giving slowed between September and June. Now that most Members’ primaries are over, they should be in a better position to write checks, he said.

“We think if you are part of a team, you have to participate,” said Matsui. “You can’t let a person off the hook.”

Matsui said he and Pelosi will try to impress upon Members that with five months to go, “even some of the skeptics believe it’s possible” to win back the House. Herseth’s win last week was the second special-election victory for House Democrats this cycle and is viewed by some as a symbol of party momentum heading into November.

Democratic targeting expert Mark Gersh has been invited to explain what he considers the Democrats’ pickup opportunities in individual districts.

“At least they aren’t saying it can’t be done,” Matsui said of the pundits. “There’s an opening and we really need to have a good year.”