WASHINGTON — With studies suggesting that long lines at the polls cost Democrats hundreds of thousands of votes in November, party leaders are beginning a push to make voting and voter registration easier, setting up a likely new conflict with Republicans over a deeply polarizing issue.

White House officials have told Congressional leaders that the president plans to press for action on Capitol Hill, and Democrats say they expect him to highlight the issue in his State of the Union address next week. Democrats in the House and Senate have already introduced bills that would require states to provide online voter registration and allow at least 15 days of early voting, among other things.

Fourteen states are also considering whether to expand early voting, including the battlegrounds of Florida, Ohio and Virginia, according to FairVote, a nonprofit group that advocates electoral change. Florida, New York, Texas and Washington are looking at whether to ease registration and establish preregistration for 16- and 17-year-olds.

Several recent polls and studies suggest that long waiting times in some places depressed turnout in 2012 and that lines were longest in cities, where Democrats outnumber Republicans. In a New York Times/CBS News poll taken shortly after Election Day, 18 percent of Democrats said they waited at least a half-hour to vote, compared with 11 percent of independents and 9 percent of Republicans.