Yes, and no. How we answer depends totally on how we are using the word “could.” Augustine explored the issue well, and both Luther and Edwards followed after him in distinguishing two different kinds of abilities. We could say that Jesus had the liberty to sin, but did not have the ability, or alternately, that He had the ability but not the liberty.
The freedom, or the “yes” of the answer comes down to this- there was no outside force restraining Jesus from sinning. It’s not as though if He had tried to speak a stone into bread during His temptation that His lips would not cooperate. There are situations where outside forces do take away our choices. When I was arrested outside an abortion mill in 1989 the police restrained me with cuffs, ran an ax handle under my armpits, lifted both ends and dragged me on to a waiting bus. There was no option where I could stay in front of the door to the mill.
The no, or the “inability” of Jesus to sin isn’t an external restraint, but an internal one. The reason Jesus could not have sinned from this perspective is that He did not want to. Jesus was without sin, altogether righteous. His sole, ultimate desire was to do the will of His Father in heaven. Given that unshakable and immutable desire, there is no way that He could have chosen sin.
Some have argued that the nature of the incarnation precludes the possibility of His sinning. Others have argued that the promises, the plan of God would preclude the possibility of His sinning. I would argue in the first instance that while the incarnation is vitally important as a doctrine, it doesn’t force the issue one way or the other. The Father and the Spirit can, and cannot sin in just the same way. That is, there is no power above them that forces them not to sin. But there is an utter lack of desire to sin within them. The same is true of the saints in heaven however. Which means the principle applies to deity, to humanity, and to Jesus in His incarnation. On the certainty of God’s promise, they certainly are sure. And it was sure that Jesus would fulfill His calling. But the certainty of the promise isn’t the means by which Jesus kept from sin. Rather it is His pure, sinless nature.
Does this make the test a farce? Again, yes and no. From one perspective, the devil didn’t have a chance. Had I been able to make a bet on the outcome I would have gone all in without a moment’s doubt. But the reason it wasn’t a farce is precisely because it was a test of His character. The reason I would have had no fear is because of His character. Jesus is the Holy One, the lamb without blemish, the true Son. And we who are in Him, to the everlasting glory of the Father, are the same. He could no more have failed than He could now let us go. Give thanks.
