Palpatine needed an external threat to consolidate his rule

[Galvatron]

My belief is that Palpatine's support in the Imperial Senate had eroded considerably between ROTS and ANH following the end of his "victory honeymoon," the institution of ever-stricter policies in the name of "peace and order," and scattered reports and rumors of atrocities in the outer systems.

But I also think this is what he anticipated, which is why he knew that he needed the Death Star to slap down any attempt at open rebellion by the disgruntled Senate.

[Crown]

I do think Palpy didn't directly have majority of the senate in his pocket. It's impractical due to the sheer number of senators. The senate is divided into parties (or similar groups) IMO, because individual senator needs backing from others to get his motions passed. If Palpy has the leaders of these parties under his control, he can manipulate a large portion of the senate.
As an added bonus, he can appear as the good guy by pointing the finger at the party leaders if things get sour.

Yes, Palpy could have become a dictator by military might, but that would have meant an another war. Palpy didn't want to appear as the bad guy, until he didn't need to give two shits about public opinion. The senate was needed to keep the wheels rolling until Palpy had his governors in place to take control. This happened at the beginning of ANH.

-Gunhead

The RotS novelisation, as well as 'The Last of the Jedi' books, make it clear that Palpatine had a super majority in the senate (through various means, we must remember that he is still hugely popular during RotS).

Whether this holds true for latter on (say approaching ANH) is immeterial since;

1. He has already consolidated his power via military rule.
2. And the Senate is essentially even more toothless than it was proceeding up to, during, and immediately after RotS.

Which is saying a damn lot, since these morons are the brain trust that first gave him emergency powers, and then elected him dictator for li- sorry I mean Emperor in the first place.

[Galvatron]

The RotS novelisation, as well as 'The Last of the Jedi' books, make it clear that Palpatine had a super majority in the senate (through various means, we must remember that he is still hugely popular during RotS).

Whether this holds true for latter on (say approaching ANH) is immeterial since;

1. He has already consolidated his power via military rule.
2. And the Senate is essentially even more toothless than it was proceeding up to, during, and immediately after RotS.

Yet, in ANH, high-ranking military officers openly fret about the senate and their growing support for the rebellion.

Given the powerful defenses of worlds like Alderaan, it's my belief that the Emperor wanted to avoid having hordes of angry senators returning to their home systems in disgust, firing up their impenetrable planetary shields and declaring open hostilities against the Empire before the Death Star was ready.

Which is saying a damn lot, since these morons are the brain trust that first gave him emergency powers, and then elected him dictator for li- sorry I mean Emperor in the first place.

Presumably not, given that Leia was a member by the time of ANH. Seems to me there was at least some turnover in the Senate since ROTS given the way Vader, his aide, Tagge and Tarkin spoke of it.

As I mentioned earlier, 20 years of draconian policy changes may have softened his support base significantly.

[Crown]

Yet, in ANH, high-ranking military officers openly fret about the senate and their growing support for the rebellion.

Given the powerful defenses of worlds like Alderaan, it's my belief that the Emperor wanted to avoid having hordes of angry senators returning to their home systems in disgust, firing up their impenetrable planetary shields and declaring open hostilities against the Empire before the Death Star was ready.

I understand your point, but it is moot. The DS allowed them (the Empire) to pumel a planet's defence in seconds, rather than the standard (what, hours/days). It's not as if - any - group/senator/sector/planet/etc could go toe to toe with the Empire anyway even before the DS.

So quite clearly those high-ranking military officers were either wrong in their grasp of politics, or right in realising that they would now be playing a second fiddle to Tarkin's DS.

Presumably not, given that Leia was a member by the time of ANH. Seems to me there was at least some turnover in the Senate since ROTS given the way Vader, his aide, Tagge and Tarkin spoke of it.

And yet, Mon Mothma was still there. And if anything, it appears Leia got the job because it would have been detrimental to Bail's health to show his face on Coruscant at some point.

As I mentioned earlier, 20 years of draconian policy changes may have softened his support base significantly.

If you wanna play that game, then 20 years of propaganda can also do wonders to his support base (see the radical shift of the view of Jedi post RotS - 'holovids' that make them out to be vampires and such). But as I have mentioned before, Palpatine used many methods to ensure he had his majority in the senate, ranging from simple popularity (mob rule), to blackmail or threat of grevious bodily harm.