Although roughly 6 million U.S. citizens are eligible to vote oversees using absentee ballots — many of whom are serving in the military — only a fraction of their ballots are being counted.

The bipartisan Election Assistance Commission found that of the nearly 1 million absentee ballots sent out for the 2006 election, only 300,000 actually were counted. Some estimate the low return of absentee ballots meant 400,000 service members' votes overseas weren't counted.

The problem seems to be the mail. It takes 18 days for the U.S. Postal Service to deliver mail to Iraq and 18 days for it to be returned.

Sen. John Cornyn, R-Texas, has introduced legislation that would allow absentee ballots to be sent via Federal Express to those serving in the military, although there reportedly is resistance from the postal union.

"It should be a national scandal that, here, our men and women in uniform who are protecting our freedom who are exposing themselves to harm are being denied the most basic civil right, and that is the right to vote," Cornyn said.

Cornyn has 29 co-sponsors to his Military Voting Protection Act, all of them Republican.

"I think its really a lack of focus and attention by the federal government," Cornyn said. "And, I think, the Department of Defense bares a special responsibility and my legislation's designed to see them discharge it to make sure that those votes count. ...

"This is something that if most Americans knew existed, the current dismal state of actual opportunity to see your vote count for our men and women in uniform, they would be up in arms."

But Defense Secretary Robert Gates said he didn't realize there was a problem.

"I think we have a significant responsibility to encourage our men and women in uniform to vote and to enable them to vote. And so this is a high priority, and your question prompts me to go find out if things are on track ... as I have been told they are in terms of making sure that we have the ballots and things available for our — for our troops," Gates said.

Cornyn sent a letter to Attorney General Michael Mukasey Friday demanding the Department of Justice investigate whether the Department of Defense is doing all it can to assist military voters, especially those overseas.

In the letter, Cornyn writes:

— Only 16.5 percent of the 6 million eligible military and overseas voters requested an absentee ballot for the November 2006 election.

— Only one-third of the requested ballots were cast and counted.

— And, 5.5 percent of the total eligible military and overseas citizen voters cast a ballot in the November 2006 election.

The Defense Department Inspector General found that less than half of the troops knew who provided voter assistance to their units and how to get absentee ballots.

But, when FOX News tried to log onto the Federal Voting Assistance Program, a website administered by the DoD, to obtain an absentee ballot, the process looked simple.

Senator John McCain is supporting the measure, and Senator Barack Obama, while not signing onto Cornyn's measure, has pushed for more to be done to allow wounded veterans to vote — another group that is effectively being disenfranchised.

FOX News' Justin Fishel and Trish Turner contributed to this report.