Q:

How to use "etherscan" to push a raw transaction without running a node?

According to this answer, how to use etherscan to push a raw transaction without running a node? In this case, do not we need to install Parity or geth or any Ethereum client ?

A:

Edit:
As Raghav Sood correctly stated, etherscan indeed has a REST-api for sending raw transactions. My guess is, that after signing the transaction and serializing it, you should take the hex output of the serialization and send it to this API. This would be the final step:
var serializedTx = "0x" + tx.serialize().toString('hex'); 

There should be enough information on the net on how to construct and sign a transaction before getting to this last necessary step mentioned above.

̶t̶̶o̶̶ ̶̶m̶̶y̶̶ ̶̶k̶̶n̶̶o̶̶w̶̶l̶̶e̶̶d̶̶g̶̶e̶̶,̶̶ ̶̶t̶̶h̶̶e̶̶r̶̶e̶̶ ̶̶i̶̶s̶̶ ̶̶n̶̶o̶̶ ̶̶w̶̶a̶̶y̶̶ ̶̶t̶̶o̶̶ ̶̶u̶̶s̶̶e̶̶ ̶̶e̶̶t̶̶h̶̶e̶̶r̶̶s̶̶c̶̶a̶̶n̶̶ ̶̶f̶̶o̶̶r̶̶ ̶̶t̶̶h̶̶i̶̶s̶. But infura is the way to go. 

register
set your infura link/key as web3 provider
get familiar with the usage of sending self signed transaction,
which you will need to provide all the neccessary parameters for and sign it with a key. 

