Does the AI ever change rersearching midway through?

If a tech win is close enough, I'd even ride out a stomping by an AI...I don't foresee the AI being any different.  You may need to try and fast-buy enough troop ships and target their high research planets to try and cripple their progress on the tech.  However, complete annihilation of the Dregin will need to be done so that this doesn't happen again in 3 weeks.

I was once trying to race the Alterains to the finish line.  They were researching Tech Victory and I was going for Ascension in TA.  My spies weren't cutting it and I ended up reloading my game a few times until I found a way to beat them by a few weeks.  It involved a ton of quick buys and practically emptying my planets to try and take down their research planets.  I turned a game that was going to be lost by 15 weeks into a win by even less.

So that said, unless you are on the verge of winning, you will need to decimate the Dregin.  I think the only time they hop away from a tech is in the plague/disease events.

 Thanks for the info. I figured they wouldn't change. But i thinkits just an AI thing that once they choose a tech they can't or just don't change it. This was one of the reasons that Mumblefratz once said a slow tech speed will hurt the AI more than the player.

When i realized that they were even touching that brack i made sure i always had the tech they were on. After each tech the would just off that branch. For instance, after Galactic Understanding the went fopr Starbase Fortification III. So now they are on Tech Victoray and will get it in 7 weeks. With my research slider around 50% i'll get it in 5. So winning isn't the problem but the poor score that win will get me is. I have 3 transports and a few ships near them but I don't think the couple of weeks it might buy me is going to do much for me. I'm going to land my transports to get the population back into the game and just hit end turn. Looks like its a tech win for me.