To take a step and affect the balance of power
To play a critical or influential role
Neutral
她是本地政坛举足轻重的人物 | Tā shì běndì zhèngtán jǔzúqīngzhòng de rénwù
She is one of the most influential figures in local politics
[Source]
一支排球队里，主攻手具有举足轻重的作用 | Yī zhī páiqiú duì lǐ, zhǔgōngshǒu jùyǒu jǔzúqīngzhòng de zuòyòng
The outside hitter is the most crucial position on a volleyball team
[Source]
None
None
This is an HSK chengyu
Lots of history for this story. The first thing to know is the timeline of the Hàn Dynasty (汉). Depending on where you look, you'll see some sources say that the dynasty lasted from 206 BC - 220 AD, while other sources will split the dynasty into the western/former Hàn (206 BC - 8 AD) and the eastern/later Hàn (25 - 220 AD). (And some will give different end and start dates than those!) This is because an official named 王莽 (Wáng Mǎng) usurped power from a weakened western Hàn and founded the Xīn Dynasty (新) in 8 AD.
The new dynasty didn't last very long — a series of environmental catastrophes and ineffective economic policies soon launched the newly-founded government into a civil war, with various armies from all over the country rising in rebellion. The most notable of these armies were the 绿林军 (multiple pronunciations, can be lǚ lín jūn or lù lín jūn) and the 赤眉军 (chì méi jūn, or the "Red Eyebrows").
It was the 绿林军 that managed to defeat storm the Xin capital and kill 王莽. Their leader, 刘玄 (Liú Xuán), had declared himself emperor some time before the final battle, and he then assumed control over the empire.
However, his control only lasted about a few years. The 赤眉军 rose up against the empire, killed 刘玄, and established 刘盆子 (Liú Pénzi) at the head of the empire.
That didn't last very long either. 刘秀 (Liú Xiù), who had served under 刘玄 but who had split with him before he assumed the throne, assembled his forces to attack the 赤眉军. The 赤眉军 was forced to surrender, and 刘秀 declared himself emperor of the Hàn Dynasty. This "later" Hàn dynasty went on to last another two hundred years.
《后汉书》(Hòu Hàn Shū, "History of the Eastern Han") by 范晔 (Fàn Yè)
Please read the notes before reading this story
There once lived a man named 窦融 (Dòu Róng, 16 BC - 62 AD). As the Western Hàn Dynasty was in its waning years, he served as a government official. When 王莽 assumed throne, he served as an important general in the military. After 王莽's death, he served under 刘玄 (Liú Xuán) as a provincial governor. When 刘玄 was eventually defeated, 窦融 amassed control and gained a large number of troops under his command. When he eventually saw that 刘秀 had reinstated the Hàn Dynasty, he declared loyalty to him. In return, 刘秀 granted him a title, and told him that he had a "举足轻重" influence.