After the very, very close presidential election in 2000, when results were in doubt for weeks, Congress appropriated funds to help states modernize their voting. And companies that manufacture voting machines have rushed new computerized systems onto the market. But there are concerns about the new machines. Apart from the inevitable glitches and new equipment, critics raise questions about machines that have no paper record of votes and about the possibility that computerized systems could somehow be reprogrammed to change votes, perhaps even change the outcome of an election.

Tuesday was Pennsylvania's primary election. In the town of Pottsville, they used brand new voting machines manufactured by a company called Diebold. Pottsville is home to a Yingling and it's the county seat of Schuylkill County. Generally, voters in Pottsville liked their new Diebold machines.

Unidentified Woman: Did you see the machine before?

Unidentified Man: No.

Unidentified Woman: So push that button. Here's your actual voting page.

Unidentified Man: Just (unintelligible) vote?

Unidentified Woman: Right. Say you want that. If you don't want him, just touch it again and it erases.

Unidentified Man: Okay.

Unidentified Woman: So we have to stand back.

Unidentified Man: I found it relatively easy to use and different screens could help you go back and forth if you needed to change anything. And I thought it was very helpful, and a step forward for progress here.

Unidentified Woman: Well, it seems funny, you know. It's sort of awkward, 'cause you're use to the paper, but now I would rather do it this way.

Unidentified Man #2: 'Cause you're in the booth there and it was dark.

Unidentified Woman: And you're closed in.

Unidentified Man #2: That's right.

WERTHEIMER: Election judge Izzy Adams(ph) at Precinct 51 said things were going better than she'd expected with touch screen voting machines. But in late afternoon, when another election official appeared with the Diebold pamphlet and pin number, Ms. Adams didn't know what she was suppose to do with it.

Ms. IZZY ADAMS (Election Judge): Did you see 051606? That's a pin number. Now where did they get, see there's a lot of things yet we don't know about these. She never mentioned pin word or password, did she? Do you remember her...

Unidentified Woman No. 2: No, I don't remember, no.

Ms. ADAMS: No, I don't remember her saying anything about password or pin number.

WERTHEIMER: Several weeks ago, the nonprofit watchdog group Black Box Voting.org raised questions about the Diebold TSX. That's the machine Pottsville is using. A computer expert hired by the group reported that the machines were designed with a portal, a significant security vulnerability. Diebold spokesman Mark Radke(ph) says it is there, but it's there for a good reason.

Mr. MARK RADKE (Diebold Spokesman): When a new version of software must be loaded on the unit because of election law changes and items like this that might take place during the life of the equipment, those new versions of software are uploaded into the system through this path.

WERTHEIMER: So the portal, the door into the system, is there to update it?

Mr. RADKE: That's correct.

WERTHEIMER: Others say that may be so, but it's also a real security threat.

Professor AVI RUBIN (Johns Hopkins): I believe that this is not only the most serious security problem that I've seen in a voting machine, but I can't think of a security problem that I've seen in any kind of system that is severe as this.

WERTHEIMER: That is Johns Hopkins computer science professor Avi Rubin. He's been studying the technical aspects of the electronic voting systems since 1997. He says that Tivo, a home device that records television shows, has tighter security than the Diebold machine.

Mr. RUBIN: Now, the reason that this is a security concern is that they made it very, very easy for someone to modify that software. So easy, in fact, that all you really need is a few seconds of physical access to the machines. You could introduce something by putting a memory card inside of them that would cause the machines to be unusable without hardware repair.

WERTHEIMER: But all of these things are not networked, right?

Mr. RUBIN: Right.

WERTHEIMER: So if you got into one machine and changed things, that would be one machine in one precinct.

Mr. RUBIN: Despite the fact that the machines are not networked, you could change the software on there so that it would put a virus on the on the memory card. The memory cards are transferred from one machine to the other.

And so the thing to keep in mind is that the virus or the malicious software that's introduced, it could cause the machines to fail, but it could also do something that would be undetectable. What if the malicious software simply said, if we're in a precinct that votes a particular way that we don't like, swap 10 percent of the votes.

WERTHEIMER: Diebold's spokesman Mark Radky(ph) says that cannot happen because poll workers see to it that voting machines are securely locked away. And before each election, the machines are retested and marked with special security tags.

Mr. MARK RADKY (Diebold Spokesman): It's a very simple and clear way to validate that, yes, that unit has been tested, it is secure and it can be used for the election.

WERTHEIMER: So what you're saying is that you can secure the machines, but there is nothing inherent in the machine to protect it from being tampered with if somebody happened to be able to get at it.

Mr. RADKY: Well, if someone has direct access to a unit, just like with your PC as an example, if someone had direct access to your PC over an extended period of time, which you wouldn't let that happen, obviously, they could, you know, remove the hard drive, put a new hard drive in and so on. And unless you tested it, you would never know.

In this situation, though, every one of the voting stations is tested before every election, it's locked down as far as the security tags are concerned, and it goes through extensive testing before the memory cards are locked into the unit.

Mr. RUBIN: I don't buy that at all.

WERTHEIMER: Security expert Avi Rubin worked with Diebold machines in Maryland.

Mr. RUBIN: I worked as an election judge and I spent a whole day with these machines. At the end of the day I collected the memory cards out of them and held them all in my hand and fed them into the accumulator machine. That's how the Diebold system works. You put all the memory cards into one machine and it counts the votes off of all of them and totals them.

It would have been extremely easy for me to have another memory card, these are very small cards, up my sleeve and stick it in the machine for five seconds. And that's all I would have to do to infect the entire precinct and compromise that election.

When you take hundreds of thousands of voting machines across the country being protected in sometimes absolutely ridiculous ways like having poll workers take them home overnight, which does happen, and you tell me that the security of the whole election depends on nobody getting a few seconds of access to that machine, I think that's crazy.

WERTHEIMER: The other issue frequently raised about new equipment, including the machines Pottsville used, is that if tampering did take place there would be no way to recount the election, no record at all of how each voter voted, and at least one state has already decided that won't work.

New Mexico has a new law mandating paper ballots, which are then electronically scanned and counted. Governor Bill Richardson pushed for the new law because New Mexico had all kinds of difficulties with touch screen equipment in 2004, making it one of the last states to report results.

Governor BILL RICHARDSON (New Mexico): We became one of the laughing stock states in the country because we had these technological machines that were not working, that in several counties were defective, were slow, were unreliable, and I basically said to myself I'm not going to go through this again. And I just think that the paper ballot system, as untechnical as it seems, is the most verifiable way we can assure Americans that they're voting and their vote is counting.

WERTHEIMER: Governor Richardson told us he expects to see other states follow his lead and go for a hybrid system with paper ballots that can be tallied quickly by computers, or if necessary, more slowly by people.

But let's go back to Pottsville, PA and to people voting at the West End Hose Company Firehouse.

Unidentified Man #3: (unintelligible)

WERTHEIMER: There were a few glitches there and elsewhere around the state. In the Pittsburgh area, machines manufactured by a competitor, Electronic Systems and Software, refused to start in many polling places, and there were similar mechanical problems in Philadelphia. Those occurred with yet another voting machine manufacturer, Danaher.

This Tuesday, Arkansas holds its primary. All but three counties will use new voting machines from Electronic Systems and Software.