In the following sentence, what does "doubled down" mean exactly?

BYD, sometimes referred to as China's Tesla, doubled down on all-electric by adding a second model to its line-up.

BYD, a Chinese carmaker, has brought a second all-electric model to the market. This shows that BYD is determined to continue with its all-electric strategy, even though going all-electric is considered risky.

Although the concept of electric cars has been around for years, decades as a matter of fact, most cars still run on petrol or gas. Carmakers haven't gone all out on electric vehicles despite of the obvious benefit of using electricity to power a car. Electricity is considered a form of clean energy, relatively speaking and therefore environmentally friendly.

But electric cars haven't proven to be a success market-wise. That's why most carmakers don't mass produce them. Not yet. That's why investment in electric vehicles is still considered risky.

We can also infer that going all-electric is risky business from the phrase "doubled down" itself, because "double down" is originally a gambling term. In gambling, one's good luck may come and go, but the risks are always there.

Anyways, round the gambling table, to double down means for a gambler to double his or her bet. If they have initially put 100 dollars on the table earlier in the game, for example, they now add 100 dollars more to the stake, therefore assuming twice as much risk as before. In other words, they're not backing down in face of greater money-losing risks.

Whether the gambler wins twice as much in return is moot. Here we are just making certain that "double down" as a gambling term is by berth fraught with risks. So metaphorically speaking when someone doubles down on a certain project, we understand he or she is redoubling their effort in pursuit of a certain risky object or goal.

It means they're pushing even harder or have become more dedicated, determined and resolute in spite of the risk or, for that matter, danger or controversy involved. They're just not backing off when perhaps they should, when most people would, that is, if common sense always prevails.

Read the following media examples for a better idea:

1. It's been eight months since I last wrote about medical marijuana, apologizing for having not dug deeply into the beneficial effects of this plant and for writing articles dismissing its potential. I apologized for my own role in previously misleading people, and I feel very badly that people have suffered for too long, unable to obtain the legitimate medicine that may have helped them.

……

Since our documentary "Weed" aired in August, I have continued to travel the world, investigating and asking tough questions about marijuana.

I have met with hundreds of patients, dozens of scientists and the curious majority who simply want a deeper understanding of this ancient plant. I have sat in labs and personally analyzed the molecules in marijuana that have such potential but are also a source of intense controversy. I have seen those molecules turned into medicine that has quelled epilepsy in a child and pain in a grown adult. I've seen it help a woman at the peak of her life to overcome the ravages of multiple sclerosis.

I am more convinced than ever that it is irresponsible to not provide the best care we can, care that often may involve marijuana.

I am not backing down on medical marijuana; I am doubling down.

-- 'I am doubling down' on medical marijuana, by Dr. Danjay Gupta, CNN.com, March 6, 2014.

2. Robert E. Murray, the mine owner who has vowed to be the "last man standing" in U.S. coal, has for the first time purchased foreign assets as his peers struggle to survive an industry downturn.

Murray Energy Corp. bought Colombian assets including mines and a port from Goldman Sachs Group Inc. and partnered with two former Goldman Sachs executives to market the fuel, the St. Clairsville, Ohio-based company said in a statement.

Murray, who founded and runs the company that bears his name, blames President Barack Obama's environmental policies for undermining coal. The acquisition is the latest in a series of deals the fourth-generation miner has made as he expands his operations amid the sector's worst downturn in decades.

"As the United States coal industry continues to be under attack for elimination by the Obama administration, we must look to international markets to ensure our survival," Murray said in the statement.

……

U.S. miners are fighting to stay afloat in the face of cheap natural gas that's upended the fuel's dominant position in electricity production, a trend being hastened by tougher emissions standards at power plants. Meanwhile, China has curtailed imports of coal, catching several U.S. producers off guard after they invested billions to increase their footprints earlier this decade when coal prices surged.

Alpha Natural Resources Inc., once the country's second- largest coal miner by revenue, filed for bankruptcy protection earlier this month after losing almost all of its value since 2011. Patriot Coal Corp. and James River Coal Co. have both filed for bankruptcy twice. Arch Coal Inc., the second-largest U.S. coal miner by tonnage, is struggling to restructure some of its debt and stay listed on the New York Stock Exchange after losing 96 percent of its value in the past year.

Murray remains the outlier. While maintaining that the U.S. coal sector is doomed, he's doubled down on buying mines. In December 2013 Murray spent $3.25 billion to acquire the West Virginia coal operations of Consol Energy Inc., and this spring he bought a stake in rival Foresight Energy LP, which operates in Illinois.

Now, the 75-year-old is looking abroad. Murray is picking up two developed surface mining operations in Colombia, the La Francia and the El Hatillo mines, as well as three undeveloped mines, more than 184 million metric tons of coal reserves, a coal port facility and railway assets, the company said.

-- Murray Energy buys Colombian coal mines, The Salt Lake Tribune, August 15, 2015.

3. The White House on Tuesday doubled down on President Trump's bizarre and debunked claim that massive voter fraud cheated him out of a popular vote victory — and the new leader's chief spokesman said Trump wouldn't rule out requesting an investigation into the bogus claims.

"He continues to maintain that belief based on studies and evidence that people have presented to him," Trump's Press Secretary Sean Spicer said during his second-ever daily press briefing when asked about reports the commander-in-chief told legislative leaders earlier this week that millions of illegal votes helped Hillary Clinton win the popular vote.

"As I noted, he's believed this for a long time … it's a long-standing belief that he's maintained," Spicer said.

"He believes what he believes based on the information he's been provided."

The phony charge — which Trump first made on Twitter while he was President-elect — has been debunked by state election officials and decried on both sides of the political aisle, but Trump is sticking by his guns.

Despite the belief in massive voter fraud, Spicer said Trump had no concerns that the phony votes affected his Electoral College tally.

"He won overwhelmingly with 306 electoral votes, the most since any Republican since Reagan," Spicer said.

Reagan's Republican successor, George H.W. Bush, actually nabbed more electoral votes than Trump as well — 426.

-- White House Press Secretary Sean Spicer doubles down on Trump's debunked claim about voter fraud, won't rule out investigation, NYDailyNews.com, January 24, 2017.

☑ Writ large=at large?

☑ Going nuclear：放绝招

☑ Priming the pump：为经济增长助力 

☑ Golden handcuffs：金饭碗

☑ What’s whataboutism?：那你呢？

☑ Dyed in the wool：榆木脑袋

☑ Sound and fury：空洞无趣