(CNN) -- With the dust having finally settled after the prolonged Democratic presidential primary, a new poll shows Sens. John McCain and Barack Obama locked in a statistical dead heat in the race for the White House.
With just over four months remaining until voters weigh in at the polls, the CNN/Opinion Research Corporation survey out Tuesday indicates that among registered voters nationwide, Obama holds a 5-point advantage over the Arizona senator, 50 percent to 45 percent.
That represents little change from a similar poll one month ago, when the presumptive Democratic presidential nominee held a 46 to 43 percent edge over McCain.
CNN polling director Keating Holland notes that Tuesday's survey confirms what a string of national polls released this month have shown: Obama holds a slight advantage over McCain, though not a big enough one to constitute a statistical lead.
"Every standard telephone poll taken in June has shown Obama ahead of McCain, with nearly all of them showing Obama's margin somewhere between 3 and 6 points," Holland said. "In most of them, that margin is not enough to give him a lead in a statistical sense, but it appears that June has been a good month for Obama."
But the new CNN/ORC poll shows that the race gets even tighter when the two most prominent third-party presidential candidates are considered.
In a four-way matchup that includes independent candidate Ralph Nader and Libertarian candidate Bob Barr, Obama's lead over McCain dwindles to 3 percentage points, 46 percent to 43 percent. (Nader registers 6 percent, and Barr gets 3 percent.)
But it remains unclear just how much effect Nader and Barr will have on the election, as summertime surveys often overstate the eventual Election Day showing of third-party candidates.
"A useful rule of thumb is that third-party candidates in November get no more than half the support polls show them having in June or July," Holland said.
Meanwhile, one day after the Illinois senator sharply defended his devotion to America during a high-profile speech in the crucial swing state of Missouri, the new survey shows that some voters continue to have lingering questions about his patriotism. The poll was taken before Obama's Monday speech.
One-quarter of all registered voters say Obama lacks patriotism, according to the poll. That breaks down to 10 percent of Democrats, 29 percent of independents and 40 percent of Republicans who say Obama lacks patriotism.
But it's likely the issue will not have a significant impact this fall.
"Strategically speaking, the question is not how many people consider Obama unpatriotic, it's how many people consider Obama unpatriotic who would have voted for him otherwise," Holland said "Most of the respondents who think Obama is unpatriotic are Republicans. That indicates that Obama may not have lost a lot of votes -- so far -- on this matter."
McCain, a former Navy pilot and prisoner of war in Vietnam, is viewed as being patriotic by 90 percent of all registered voters.
The poll, conducted June 26-29, surveyed 906 registered voters and carries a margin of error of plus or minus 3.5 percentage points.