EVANDALE, Ohio (CNN) -- John Dyer remembers being unable to sleep.
For Sen. John McCain, Ohio could be a critical proving ground in his effort to win war-weary voters.
"I woke up at 4 in the morning and walked around the neighborhood. Part of my mind was just torn with anger. I wanted to go to Iraq and find those people who had done this and kill them," he said.
Two and a half years have passed since the knock on Dyer's door. The Marine flag still flies outside his suburban Cincinnati, Ohio, home, the Gold Star banner in the window a reminder of the message delivered by two Marines that August day.
The pain is constant, but some things have changed.
"I do think in hindsight going into Iraq as we did was a huge mistake," John Dyer told CNN during a visit this past week. "I thought it sounded like it was necessary at the time."
Lance Cpl. Christopher Dyer was 19. His father's grief is shaped by his constant study of news and information about the war, and his son's last few phone calls from the war zone.
"They were worn out and there weren't enough of them," John Dyer said.
A onetime war supporter is now a war critic. Yet in Tuesday's Ohio primary, and again in November, Dyer is supporting the candidate who insists things are finally improving in Iraq, and who insists the troops must stay to finish the job.
For Sen. John McCain, Ohio will be a critical proving ground in his effort to win war-weary voters. Watch as McCain speaks out on Iraq while campaigning in Ohio »
"Seems like we have shown a lot of progress and I don't think it is time to quit and run," Dyer said. "And I think if we hadn't shown some progress, it would be time to call it a day. .... I hope people who think we should just cut and run or get out as quickly as possible will at least listen to Sen. McCain articulate the reasons why he wants to do the things he wants to do."
Americans do see some progress.
In the latest CNN/Opinion Research Corp. polling on the Iraq war, 46 percent of Americans say things are going well in Iraq, up from 34 percent in November.
In that same survey, 34 percent of Americans support the war; 63 percent oppose it.
The numbers reflect the challenge McCain will have selling his position in the fall election campaign, and reflect what Dyer hears from friends and colleagues he said are generally reluctant to discuss the war in his presence.
"I think I am in a minority view," Dyer said. "My friends and people who know me are obviously very guarded about talking to me about this, for obvious reasons. But what I sense is people are just dog tired of the situation and, I don't know what to compare it to, but something you are just tired of messing with."
No Republican has won the White House without carrying Ohio, and the unpopular war is one of the factors in big recent Democratic gains in the state.
"In 2006, independents moved over to the Democratic Party in Ohio," said Eric Rademacher of the University of Cincinnati.
Rademacher, the co-director of The Ohio Poll, added: "If there is a concern for the Republican candidate, that's it: That they need to make a move to bring back those independents over to the Republican side in order to swing the difference in Ohio."
McCain's effort included a visit Wednesday to an Ohio company that makes armored vehicles the senator credited with keeping troops in Iraq and Afghanistan safer. After a tour of the assembly line, McCain told company employees:
"I would like to tell you this challenge will go away. But as you know I am known for straight talk."
Dyer made his decision before our visit, but said he did some research on the Clinton and Obama campaign Web sites.
"I don't understand their position at all," Dyer said. "I think we are already talking about bringing combat troops home. We are talking about a difference in the pace."
He is soft-spoken, and considers his words carefully.
Near the end of our discussion, this question: "Do you ever worry because you did pay a price, and a very painful personal price, that your judgment is clouded?"
After a pause, "Yup. Yes. I can almost guarantee you my judgment is impacted by that," Dyer said slowly. "I try as hard as I can to separate my personal loss ... I know it is not really possible." E-mail to a friend