for sure, Senna didn't want Warwick as it would mean lotus having to fund 2 cars going for the title, and he didn't believe they had the funds for it, and Dumfries was loaded.
Lotus wanted to bring Warwick in so they could have two decent drivers, as Ern said, Senna vetoed it. One story is that Senna didn't think Lotus was capable of having two front running cars, the other train of thought is that he wanted an out-and-out no.2 who wouldn't challenge him at all. Warwick was considered a very good driver and could have taken points off Senna.
I have always thought it was the latter . No biggie though , either way Senna blocked it . He was my hero , but MS is far from being the only driver who wanted a slow team mate .
I think it was more to do with the money, at the time Lotus were definitely on the downward slide financially, he'd been in the hunt for the WDC in '85, but Lotus had split the teams resources between him and Elio which he thought had cost him the chance to win it, so he wanted a guaranteed number 2. oh, and no to 38.
Another fluky guess . I will try and think of something alter today , unless anyone else can think of anything .