Story highlights New polling shows Donald Trump still riding high both nationally and in Iowa

But there are some signs his disparaging comments about John McCain might hurt him

Washington (CNN) New polling released Monday -- nationally and in Iowa -- finds Donald Trump squarely in the top tier of candidates, but raises some questions about whether he'll be able to maintain that standing.

But there are some signs Trump's Saturday remarks questioning Arizona Sen. John McCain's military service may have been a turn off to some potential voters. The poll, fielded from Thursday to Sunday, found a drop-off in support for Trump in interviews conducted on the final day of fielding. While he earned 28% support during the first three nights of interviewing, that dipped to single digits on the final day.

That shift occurred among a small sample of Republicans, so it's difficult to judge whether it will hold up as the campaign rolls on. But the poll finds other warning signs for Trump's campaign.

Just 34% of Republicans think that Trump's views reflect the core values of the Republican Party, a majority, 54%, say they do not, and 31% of Republicans say they would definitely not vote for him in the general election should he win the party's nomination. About twice as many as have ruled out a vote for Bush.

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