PHOTO: Win McNamee/Getty Images
(CNN) —  

Steve Bullock’s presidential campaign is seeking to reassure their donors with a memo that casts the race’s frontrunner as flawed and unable to defeat President Donald Trump, days before the Montana governor is not among the top 10 candidates on the primary debate stage in Houston.

Bullock so far has failed to gain any traction in the presidential primary. The red state Democrat did not meet either the donor or polling thresholds set by the Democratic National Committee for the September debate and consistently polls at the bottom of the 20 Democrats running for the party’s nomination.

But that hasn’t dissuaded Bullock, who has said repeatedly that he plans to be in the race when voters caucus in Iowa in February.

One hurdle for that plan could be money, so on Tuesday, Bullock campaign manager Jennifer Ridder sent donors and other supporters a four-point memo laying out Bullock’s path to victory and acknowledging that the governor will not be on the stage on Thursday.

A key point outlined by Ridder goes directly after former Vice President Joe Biden, by name, and Vermont Sen. Bernie Sanders, by reputation.

“Again and again, we hear from Democratic primary voters that the most important quality in a candidate is their ability to beat Trump next November,” Ridder wrote. “At the same time, there is a growing fear that the candidates promising revolutions are out of step with general election voters while others fear Vice President Biden may be unable to take down Trump.”

Ridder’s by-name knock against Biden comes as other candidates and campaigns are starting to question the front-runner. But polls have consistently shown that many of the top Democratic candidates, including Biden and Sanders, would defeat Trump in a hypothetical match-up.

Bullock, as Ridder lays out in the memo, is banking almost entirely on Iowa; the Hawkeye State is the only early nominating state mentioned in the entire memo.

Belying his smaller campaign, Bullock has 25 organizers on the ground in Iowa and has made 10 trips to the state as a candidate.

“My overall plan is it doesn’t end until the early states have voted,” Bullock told CNN during an interview in Iowa earlier this month. “So, I’m going to continue to do exactly what I have been doing hopefully I’ll be on the October stage.”

Ridder makes a similar argument in her memo, which argues voters have been largely tuned out of the Democratic race throughout the summer and will return begin paying closer attention in the following months.

“As the field winnows and as voters start paying closer attention, they’ll see Bullock is a winning choice – a Democrat with progressive values, a focus on getting things done, and solving problems in the here and now,” Ridder writes.

The issue for Bullock is, however, that conversations with Iowa Democrats found many are eager for the field to thin.

“It’s too big,” said Matt Spellman, a 49-year-old Democrat from Cedar Rapids. “It really is. I’m ready (for people to drop out). It’s getting to be too overwhelming.”

His thoughts were echoed by Lee Clancey, a former mayor of Cedar Rapids.

“We are getting to a point where we need to start winnowing the field,” Clancey said. “I would like to see people who have not broken out of the pack take a back seat.”

Ridder, like top aides from other Democrats who have missed the debate stage this week, also goes after the DNC, which opted to raise the thresholds for the September and October debates.

“The DNC inserted itself in this process in an unprecedented way,” Ridder writes in her plea to donors. “But Governor Bullock has always trusted voters (especially those in the early states) to make a careful and deliberate decision.”

CNN’s Jeff Zeleny contributed to this report