No, he’s not as poor as Palin, not as poor as Quayle in ‘88. But approaching the Quayle level.
BTW, I don't think that Palin hurt McCain very much in 2008, or that Quayle hurt Bush very much in 1988:
(1) On Palin, see my post at
https://www.alternatehistory.com/forum/threads/wi-president-palin.318975/page-3#post-9298478:
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The best study I have seen is Bernard Grofman and Ruben Kline, "Evaluating the Impact of Vice Presidential Selection on Voter Choice." They conclude
"While our general finding that the net impact of vice presidential selection is at most 1 percentage point confirms that of earlier work, our assertion that the gross impact of vice presidential selection in 2008 was very similar to (though slightly lower than) the historical average impact, and that the net impact of vice presidential selection in 2008,at about one-half of a percentage point, was also slightly lower than its historical average, may violate the common wisdom that Palin’s choice had significant electoral implications for McCain. Compared to previous elections, the difference between DR voters’ (those with preferences for Obama over McCain and Palin over Biden) and DD voters’ propensities to vote Republican was nearly the same as the period average (.11 versus .13). The difference, however, between RR voters’ and RD voters’ likelihood of voting Republican is nearly three times the historical average (.42 versus .15), suggesting that there was potential for Palin’s candidacy to have been very costly to the Republicans, if the proportion of RD voters was high. On the other hand, if the proportion of DR voters was very high, even the 11-percentage-point difference we found in 2008 could have cost the Democrats votes. The facts, however, were that DR voters represented only 2% of the sample in 2008, far less than usual, and RD voters only 5% of the sample in 2008, only negligible, even below (an already quite low) long-term average. Nonetheless, as usual, the net impact of vice presidential comparisons by voters in 2008 helped the Democrat..."
http://www.mwpweb.eu/1/76/resources/publication_522_1.pdf
In short, I do not think Palin hurt McCain very much. OTOH, I don't agree that she actually helped him. The exit poll you cite provides, as its own summary remarks, "mixed evidence.'" " Fully 60% of Americans casting ballots said that Palin is not qualified to be president should it be necessary; 81% of these voters favored Obama. Yet those who cited Palin’s selection as a factor in their vote — 60% of all voters — favored McCain by 56% to 43%." What I would like to know is this: Of those who would cite *Biden*'s selection as a factor in their vote (a question which unfortunately doesn't seem to have been asked in the exit poll, as far as I can see) how many would favor Obama and how many McCain? In short, may this not simply be a case that those who cite the choice of a vice-presidential candidate as a factor in their decision are more likely to cite him or her as a factor *for* the party to which that candidate belongs?
(Also, FWIW, of those--only 7% of the electorate--who cited the choice of Palin as *the most important factor* in their vote, 52% voted for Obama.
http://www.cnn.com/ELECTION/2008/results/polls/#val=USP00p6 Palin got her best ratings among those who called the choice of Palin a "minor factor" in their decision.)...
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(2) On Quayle, as Steve Chapman notes in "Nobody Votes for the Veep"
https://slate.com/news-and-politics/2000/06/nobody-votes-for-the-veep.html "In Gallup Polls taken every four years asking if the selection of a particular running mate or a type of running mate (a black, for example, or a woman) would make the respondent more or less likely to vote for either ticket, the invariable consensus choice is that it "doesn't make much difference." Even in 1988, 64 percent of voters said that about Quayle. Only 5 percent of those who voted for Dukakis gave Quayle as an explanation."
In the same way, I think Ryan's effect on 2012 was negligible--and so would be the effect of any other running mate, unless they got into a really serious scandal.