McCain says his naysayers within the GOP just don't like his tendency to call it like he sees it.
"I came here to Jacksonville to tell people what they want to hear," he said at a press conference at a private airport, "and sometimes what they don't want to hear."
But conservative voters don't see it quite that way.
"He doesn't always line up with what we believe in," said Chandra Judy, 34, of Orlando, who was waiting for Mike Huckabee to arrive. "I think it's not really distrust; I think they're looking at his record. When the issues came up, how did he vote?"
Her examples include McCain's support of an immigration bill, which he co-wrote with liberal icon Sen. Ted Kennedy of Massachusetts, that would have granted illegal immigrants a way to become citizens after paying fines and fees and meeting other requirements.
There are other votes, too. McCain opposed President Bush's tax cuts in 2001, and also voted against them in 2003. He said he opposed them first because they carried no companion restrictions on spending and then because the Iraq war had begun and he thought cutting taxes was ill-advised during war.
In 2006, McCain voted to extend the tax cuts because he said letting them phase out by then would have amounted to a tax increase.
But to Republicans who have watched McCain and winced, it isn't just that his positions have been bad. His timing has stung, too.
Republican consultant Brett Doster, who worked on Bush's campaigns, said McCain's public criticism of the early Iraq strategy irked administration supporters. McCain remains a vocal critic of the early strategy, and Doster said his early call for more troops still isn't recalled fondly by conservatives - even though McCain turned out to be right.
"For a lot of conservatives, there have been some real pressure points in this administration, and Republicans, as a whole, have kind of closed ranks," Doster said. "McCain was a contrarian at times when people didn't like it."
And another thing
Local Republican leaders are still smarting, too, over McCain's signature legislative victory, the McCain-Feingold Act, which sharply limited the role party money could play in federal elections.
"This really hurt McCain with all the people like me, the insiders, because we're the ones who are so affected by McCain-Feingold," said Palm Beach County Party chairman Sid Dinerstien, who is uncommitted. "But we're also the ones who vote in all the primaries and also are supposed to get out the vote. That's why he doesn't do so well in primaries."
The campaign finance law is just one of several examples of McCain working with a Democrat to advance his agenda, something McCain himself touts on the campaign trail. But for some Republican voters, McCain works just a little too easily with Democrats.
McCain was part of the so-called Gang of 14, a collection of mostly moderate senators from both parties who brokered an end to a high-stakes dispute over Bush's judicial appointments. Although the group struck a deal that helped Bush get some long-delayed judges seated, McCain's affinity for compromise wasn't entirely appreciated.