Rep. Paul Ryan starts his vice presidential campaign in not-so-great territory, with Americans rating his selection more unfavorably than any pick since at least 2000, according to a new poll.

The USA Today/Gallup poll shows 42 percent rate Mitt Romney’s selection of Ryan (R-Wis.) as “fair” or “poor,” while 39 percent rate it as “excellent” or “pretty good.”

Those numbers are worse than the initial reactions to both Dick Cheney in 2000 and Sarah Palin in 2008. And they appear to be the worst since Dan Quayle in 1988 (according to a different pollster). All three Republicans wound up being very unpopular in the following years.

Romney’s campaign quickly moved to point out that initial reactions are hardly the be-all, end-all in campaigns. And they say Ryan probably suffers from the fact that most people don’t know who he is.

“All these numbers indicate is the simple fact that Rep. Paul Ryan was not a nationally known figure prior to being named as Gov. Romney’s vice-presidential pick,” Romney pollster Neil Newhouse said in a statement.

In addition, multiple other national polls have shown views of Ryan are generally more positive than negative. A CNN/Opinion Research poll released last week showed 27 percent of Americans rated him favorably, while 19 percent rated him unfavorably, and a new Washington Post-ABC News poll shows Ryan’s favorability rising significantly after his selection, from 23 percent beforehand to 38 percent now. (Notably, his unfavorable rating ticked up just one point, from 32 percent to 33 percent.)

These polls and the Gallup poll would seem to contradict each other, but they are actually asking different things. The Gallup poll asks whether Ryan is a good pick, which is a little different than asking whether you like someone. President Obama, for instance, had a long stretch in recent years where his personal favorability numbers were significantly higher than his job approval ratings.

People liked Obama personally, even if they didn’t necessarily think he was doing a good job. In this case, people may like Ryan personally, even if they are uncertain about his Medicare plan, for example. And much of the media coverage over the weekend focused on whether that Medicare plan would be a problem for Romney, which may be why people don’t necessarily see Ryan as a good pick, politically speaking. (Other vice presidential picks, meanwhile, probably had more of a honeymoon period, since their name wasn’t so synonymous with an already-simmering political issue.)

The difference in polls could also simply be a reflection of the fact that most people simply don’t know Ryan. It’s clear that there is plenty of work to do — for both sides — in defining him, particularly over the next three-plus weeks, when opinions of him will begin to solidify. Ryan’s controversial proposal to turn Medicare into a voucher program will be Topic No. 1 in that debate.

Quayle was the only somewhat-recent vice presidential candidate to have more poll respondents rate worse than Ryan; 52 percent of likely votes in a Harris Poll rated him as a “fair” or “poor” choice. (The polls aren’t completely analogous, though, because the Ryan poll tested all adults, not just likely voters.)

At the same time, the Gallup poll shows Ryan is seen as presidential, with 48 percent saying he is qualified to be president if the situation arose and just 29 percent saying he is not. Palin’s marks on that measure were lower.

Updated at 12:37 p.m. to reflect new Washington Post-ABC News poll results.