Former Vice President Joe Biden, 2020 Democratic presidential candidate, speaks during a town hall event in Manchester, New Hampshire, U.S., on Wednesday, Oct. 9, 2019. Kate Flock | Bloomberg | Getty Images

Joe Biden's cash-strapped presidential campaign has been talking to top donors about ways to beef up its fundraising strategy in the crucial fourth quarter, including a possible increase in spending on social media platforms such as Facebook, according to people familiar with the matter. They have also discussed a bigger emphasis on text messages that ask potential contributors to support Biden's campaign, said these people, who spoke on the condition of anonymity. The former vice president's campaign already sends texts to potential backers, and it is unclear what the message will be during the quarter. The development comes at a precarious time for Biden's campaign, as his fundraising and polling numbers weaken against an onslaught from progressive Sens. Elizabeth Warren and Bernie Sanders, and fellow moderate Pete Buttigieg, the mayor of South Bend, Indiana. The former vice president entered the race for the Democratic presidential nomination earlier this year as the clear front-runner. He enjoyed commanding leads in polls and got off to a fast money-making start with $21.5 million in the second quarter. However, he pulled in only $15.7 million in the third quarter, and had $8.9 million in cash on hand — both totals well behind Sanders, Warren and Buttigieg. He maintains a 6-point lead over Warren in Real Clear Politics' national polling average, but polls of early primary states such as Iowa and New Hampshire show Biden lagging or at risk of losing. The Iowa caucuses and the New Hampshire primary, both set for February, are the first contests of the 2020 election season.

Digital grassroots struggles

Fundraising records illustrate Biden's biggest fundraising problem, namely appealing to the kinds of grassroots and small-dollar donors who fuel the Sanders and Warren campaigns. Beefing up digital efforts could help Biden's campaign in this regard. People familiar with the campaign's deliberations say boosting online efforts doesn't necessarily represent a major shift in strategy. Yet several of Biden's fundraisers believe that the campaign needs to improve its appeal to online donors. "He can do more with online voters, but he's done surprisingly well," Biden supporter and former Pennsylvania Gov. Ed Rendell told CNBC in a recent interview. Other donors have been privately questioning where they can turn for sources of campaign funding as elections in the early primary states loom over the former vice president's organization. Earlier this month, Biden and his team rallied their donors at a summit in Philadelphia by calling on them to help them succeed on Super Tuesday primaries on March 3, when 40% of delegates are up for grabs. California, North Carolina and Texas all hold their primaries that day. A Biden spokesman did not return a request for comment. Biden's campaign has been behind in spending on Facebook ads that often entice contributors. Since he entered the race in April, Biden has spent $2.5 million on Facebook. Warren's campaign has spent $2.7 million and Sanders has bought $3.1 million in ads, Facebook's ad archive shows. Since January, President Donald Trump's campaign has spent $13.6 million on the platform. Read more: Candidates love to rip Big Tech companies, but their campaigns still pay them millions Throughout Biden's 2020 run, 35% of his donors have given under $200, while almost 65% are writing larger checks, according to the nonpartisan Center for Responsive Politics. Warren has been dominating the race in capturing smaller donations, which helped her raise $24.6 million in the third quarter and finish with $25.7 million on hand.

The super PAC question