Sheldon Adelson, the biggest Republican donor, wants key GOP fundraising groups to shape up after this year's midterm wipeout in the House or risk losing his support for the 2020 election cycle, CNBC has learned.

Adelson's closest advisors are preparing to warn the heads of the GOP congressional fundraising committees that they need to make significant changes to the way they raise money if they want to see the Las Vegas Sands CEO invest in the 2020 congressional elections, according to one of Adelson's top lieutenants, who spoke on the condition of anonymity.

Adelson and members of his inner circle are frustrated with the top Republican fundraising organizations, such as the National Republican Congressional Committee, the National Republican Senatorial Committee and the Republican National Committee, particularly in the way their consultants handled being outraised throughout the 2018 midterms, according to this person.

"The money will no longer go to inefficient organizations," this person said. "You have to give them time to reform but if they are resistant to it, we will have to leave them behind."

Adelson was the top individual donor in the past election with $112 million in contributions. Less than $200,000 of that total went to the committees he's considering walking away from. Adelson gave more than $100,000 to the NRCC and more than $33,000 each to the RNC and NRSC, according to Federal Election Commission records.

Adelson's frustrations may also lead to a cutback in donations to Republican super PACs, including the Congressional Leadership Fund and the Senate Leadership Fund, said people close to the casino mogul. Adelson gave more than $40 million combined to these two PACs in 2018.

Adelson has also been a staunch supporter of President Donald Trump's and became a top financier of his during the 2016 presidential election.

Democrats are projected to gain at least 39 seats in the House, while Republicans are set to pick up two seats in the Senate. The nonpartisan Center for Responsive Politics shows that more than $5 billion was spent on this year's midterms, including $2.5 billion by Democrats and $2.1 billion by Republicans. The site also notes that the total amount raised throughout the 2018 cycle was at least $3.96 billion.

Even with contributions from Adelson and other top-tier donors, most of the Republican committees were outraised by their Democratic opponents. The Democratic Congressional Campaign Committee, a House Democrat equivalent to the NRCC, brought in $250 million, compared with the NRCC's $174 million. The Democratic Senatorial Campaign Committee saw $135 million added to its coffers this cycle while the NRSC raked in $129 million. The RNC outraised the Democratic National Committee in 2018.

Adelson and his team are disgruntled about the Republican committees' lack of a response to ActBlue, a Democratic grassroots fundraising platform.

ActBlue is an online technology fundraising organization that helps Democrats running for office, liberal interest groups and fundraising committees raise money through the internet. The online portal, which is focused on small donations, brought in more than $1 billion this year, about a third of its total haul since it was founded in 2004, records show.

The National Republican Congressional Committee, chaired by Rep. Steve Stivers, R-Ohio, during the midterms, said it has been working on a solution to ActBlue since 2017 and it's a key initiative for it going into the new Congress.

"We began in 2017 to examine how ActBlue functioned and what we could do to replicate the situation and its very much a top priority," an NRCC aide told CNBC.

Representatives for Adelson, the NRSC, and RNC did not return requests for comment.

For Republicans involved with creating a counterbalance to ActBlue, they conceded that Adelson is one of many donors who is concerned about the fundraising issues facing the party as they go into a pivotal election season.

"Sheldon, like many major donors in the party, is concerned whether or not we have the infrastructure necessary on the small dollar front. It's something he definitely wants solved," said a senior strategist involved with the planning.

This person, who spoke on the condition of anonymity, said the solution to the ongoing hurdles is being addressed by the likes of Senate Majority Leader Mitch McConnell, R-Ky., incoming House Minority Leader Kevin McCarthy, R-Calif., and White House senior advisor and Trump's son in law, Jared Kushner.

McConnell reportedly admitted at a private donor event on Capitol Hill on Wednesday that Democrats dominated their party in the online fundraising battle – and that the main obstacle was ActBlue.

These leaders along with Republican congressional aides have been in touch with a number of vendors and digital consultants in order to come up with an answer to ActBlue and those involved say they expect to craft an alternative to the Democratic fundraising site by 2020.

If they can pull it off, it could be a game changer for Republicans who will be defending at least 22 Senate seats and hundreds of positions in the House.