"We're running in a million different directions," said Alex X. Mooney, chairman of the Maryland Republican Party. The state GOP helped petition the same-sex marriage and the immigrant tuition measure to referendum, and are urging "no" votes on both.

"We would like to moderate the far-left bills from the Democratic monopoly General Assembly," Mooney said. The referendum process "provides a check and balance," he said.

Candidates in the Senate race engaged in their own last-minute campaigning Monday.

"Marylanders came out in record numbers during early voting, and I can tell that we will surpass records on Election Day, too," said Cardin, a Democrat. "You can just feel the excitement of folks who want to get out and cast their ballot because the stakes are so high for us and our children."

His opponents, Republican Daniel Bongino and independent Rob Sobhani, agreed.

"The response to our phone banks, canvassing operation and social media has been overwhelmingly supportive," Bongino said. "We are confident that we did everything in our power to win this election."

"The folks I've met will turn out to vote today," Sobhani said. "And I believe I have done my part in offering an alternative and a plan to put our state back to work."

The Associated Press contributed to this article.

john.fritze@baltsun.com

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10 things you need to know on Election Day

Have a last-minute voting question? We have answers from Maryland State Board of Elections officials Ross Goldstein, deputy state administrator, and Donna J. Duncan, director of the election management division. Here are 10 things you should know before heading to the polls:

Where do I vote?

Your local precinct. If you've misplaced the voter information card election officials mailed to you, look up your precinct online at the state Board of Elections website. Follow the "find your polling place" link.

2. What's on my ballot?

Federal, state and local issues created an unusually crowded the ballot this year. You can cast a vote for president, one of Maryland's U.S. senators and the representative for your congressional district. There are also seven statewide ballot questions, including whether to legalize same-sex marriage, expand gambling and allow some illegal immigrants to pay in-state college tuition rates. And there may be more local ballot issues unique to your area.

After you've found your polling place at the state's website, you can click on the link to see everything on your sample ballot. You can also print it out and take it with you into the voting booth.

3. How long will I have to wait in line?