As the broader digital-currency market garners wider attention, the most popular of the cohort, bitcoin, is facing its fiercest challenge for cryptocurrency supremacy in its brief history.

The No. 1 cyber asset was trading at around $15,000, but down from its mid-December peak near $20,000. Bitcoin futures for January US:XBTF8 on Cboe Global Markets Inc. CBOE, +2.14% settled at $15,055, up 3.5%, while futures US:BTCF8 traded on CME Group Inc. CME, -0.97% for the same month finished with a 2.7% gain at $14,855.

However, bitcoin BTCUSD, +0.47% , despite a late-session jump following a report on Tuesday that Peter Thiel’s hedge fund has built a large stake in bitcoin, has been under pressure from a cadre of coins that threaten to supplant it as the most used virtual asset. It is a challenge that the cryptographically produced currency hasn’t faced since its debut in 2009.

Recent surges in Ethereum’s Ether coins and Ripple Labs’s respective assets are threatening to knock bitcoin off its pedestal atop the digital currency pecking order.

According to CoinMarketCap.com, bitcoin’s share of the cyber-unit market slipped to about 36% at its nadir, representing it lowest share ever even as the total value of all digital currencies hit a record peak at about $650 billion (see chart below):

Digital currency market value rises to records.

It has been anticipated by some bitcoin bears that the asset would eventually be surpassed by Ethereum, which has been the second-most valued crypto, but a run-up for Ether coins and, recently, Ripple could see either overtake bitcoin in a switch referred to in digital-currency circles as the flippening.

Market participants say there should be little surprise that after the dazzling year bitcoin had in 2017, up 1,300%, takes a back seat to some if its slightly lesser-known rivals. Moreover, critics argue that bitcoin has a number of shortcomings that make its rivals better suited to assume the digital mantle in coming months and years.

Here are three contenders that could usurp the bitcoin king and realize the flippening (a term that has been used to describe Ethereum’s overtaking bitcoin):

1). Bitcoin Cash ($46 billion)

The biggest knocks on bitcoin are the slow speed of transaction processing and the costs incurred by digital miners in supporting the blockchain, the decentralized, record-keeping technology that underlies all cryptocurrencies.

Bitcoin cash supporters intended on fixing those problems via a so-called hard fork in August that created the bitcoin rival that today boasts a market value of $46 billion, compared with bitcoin core’s $260 billion value. In other words, bitcoin cash is about one-sixth the value its larger cousin.

Known as “Bitcoin Jesus,” Roger Ver has been a big backer of bitcoin cash, saying that it is a better tool for transacting business than the original.

2). Ethererum ($87 billion)

Ethereum, sometimes synonymously referred to as Ether, has been on a tear. Ether coins boast a total value of $82 billion. The Ethereum blockchain is noted for the ease with which software developer’s can write smart contracts atop the Ethereum protocol. Those include contracts that can help facilitate the documentation and sale of properties without a broker.

Read:This $1 million house is the first to be sold on the blockchain in the U.S.

Ethereum transactions can be confirmed in seconds by the community of miners who underpin the currency, versus minutes for bitcoin core. The allure of bespoke contracts on Ethereum also has helped to give rise to so-called initial coin offerings, or ICOs, which are often atop the Ethereum blockchain. ICOs have been a popular way of using virtual currencies to fund crypto-related ventures.

3). Ripple coins ($94 billion, or $245 billion including units owned by Ripple Labs)

San Francisco-based Ripple launched in 2012 and is unlike most of its peers. It is a centralized ledger of transactions intended to serve as a conduit for bank-to-bank payments. Ripple transactions also are measured in seconds versus minutes for bitcoin. Bitcoin purists’s biggest criticism of this rival is that it is centralized, meaning that someone still acts a third party between transactions and that the company caters to financial establishment.

Here are how some other industry participants told MarketWatch they are thinking about bitcoin’s dominance in 2018:

“Ripple’s recent meteoric surge is a particularly good example of this. Also the recent surge in Litecoin, which prompted the founder of Litecoin to sell all of his coins, is a good example of hyper speculation in less known, yet still highly liquid, cryptocurrencies. People are chasing momentum and short term gains. It’s really that simple,”—Christopher Grey, co-founder and COO of enterprise software firm CapLinked

“Some market commentators think this signifies a structural change, akin to a “flippening” in that the project isn’t keeping pace with more nimble competitors. It’s too early to tell whether this is more than short-term market noise, but one thing is for sure: Bitcoin is the most resilient project in the world and has a long history of confounding its naysayers!”—Rob Viglione, co-founder of ZenCash