Early voters line up outside a polling station in Silver Spring, Md., in October 2012. (GARY CAMERON/Reuters)

Maryland’s General Assembly is expected to reach final agreement in coming days on a measure promoted by Gov. Martin O’Malley (D) that for the first time would allow residents to register to vote and cast a ballot on the same day.

Same-day registration would occur during early voting, which under the bill would be expanded from six days to eight. In addition, the number of early voting sites would be increased.

With thousands of voters in the Washington suburbs and beyond standing in line for hours at polling places in November, the measure would also require state election officials to study how to reduce the average wait to 30 minutes or less.

Although it has been warmly received by much of the General Assembly, the legislation has been caught up, in part, over efforts to fix a provision that would allow absentee voters to receive ballots over the Internet instead of by mail.

Advocates for people with disabilities have lobbied heavily for the measure, saying it would allow those who need a lot of time to vote or who cannot vote without the help of others to do so more conveniently from home. But a group of election technology experts warned last month that the online system could be exploited on a mass scale, potentially jeopardizing election results.

The Maryland House and Senate have passed similar proposals to tighten security, and key lawmakers on Thursday predicted that a final compromise could be reached this week. But a grass-roots voting group said the proposed changes would still leave the online-ballot-delivery system vulnerable.

If approved, the system would allow any Marylander who votes absentee to receive a password by e-mail to download and mark a ballot at home before mailing it back to election officials.

Security concerns revolve around a vulnerability that election officials acknowledge in the state’s new online voter registration system. Since last year, Maryland residents have been able to use their state driver’s license numbers to register online. But in Maryland, that number is a formula of a resident’s name and birth date.

Critics say hackers could use publicly available databases and birth date information from social media sites to decode driver’s license numbers. That information, they say, could be used to assume Maryland voters’ identities and request large numbers of ballots over the Internet.

State election officials say they are monitoring the registration system for automated attacks and would spot wide-scale suspicious behavior almost immediately.

Under changes passed in recent weeks in the House and Senate, a voter would also have to provide the last four digits of his or her Social Security number before being able to register online.

The House version would also require a voter to provide additional information known only to the applicant, and it would increase penalties for voter fraud to up to $5,000 and one year in jail. In addition, the House would require the State Board of Elections to engage an independent consultant to study and make recommendations on improving security of the online absentee system.

“We had some security concerns, but I think we’re getting there,” said Sen. Joan Carter Conway (D-Baltimore), who chairs the Education, Health and Environmental Affairs Committee, which is reviewing changes made to the bill in the House.

Rebecca Wilson, co-director of the nonprofit group SAVE Our Votes, said providing the last four digits of a Social Security number would fix only the most glaring vulnerability. She said the online ballot delivery should not be used until independent security experts review the system fully.

“We don’t know what other vulnerabilities may be there that we don’t know about yet,” she said.

Part of the concern over the bill has been whether it is a first step toward moving Maryland to full online voting, something Wilson’s group fiercely opposes because the state does not verify signatures on ballots.

Conway said that it’s a logical step for the state to offer online voting but that she thinks it will be a long time before lawmakers are comfortable with the idea. “They do the registration online now,” she said. “But it will be a while in Maryland before we move to Internet voting.”

Under the legislation, the state would expand the number of early voting centers, depending mostly on county populations. Montgomery and Prince George’s counties would go from five sites to eight beginning in 2014.

Republicans have been more concerned with the same-day registration part of the bill, which would likely begin in 2016.

“I think it’s a solution in search of a problem,” said Sen. Allan H. Kittleman (R-Howard). “I don’t hear any of my constituents saying they feel left out of voting. We’ve made it pretty darn easy to register in Maryland, and having people register the same day, it is begging for abuse.”

Republicans pointed to the case of Wendy Rosen as an indication that Maryland voting rules are already lax. Rosen was the Democratic nominee in the state’s 1st Congressional District last year until she dropped out when it was discovered that she had been registered to vote in Maryland and Florida and had cast ballots in both states in recent years. She pleaded guilty this month and was sentenced to five years’ probation.

Kittleman said he is particularly worried about out-of-state college students registering in Maryland and their home states. “If a college student can walk up and vote in Maryland and also file an absentee ballot in North Carolina, who’s going to know?”