About 1 in 3 absentee ballots cast in Wisconsin so far have come from the state's largest and most heavily Democratic counties, giving Hillary Clinton's presidential campaign a reason to be optimistic about its chances here, even as polls show a tight race with Republican Donald Trump.

Clinton campaign manager Robby Mook, in a conference call with reporters on Thursday, singled out Dane and Milwaukee counties as places around the country where early voting turnout was strong.

Wisconsin voters do not register by party, so it's impossible to know whether more Republicans or Democrats are voting early. But high turnout in Madison and Milwaukee, the state's two largest and most Democratic cities, is essential for Clinton's and Senate candidate Russ Feingold's campaigns.

Numbers compiled by the state Elections Commission show that as of Tuesday, 50,883 absentee ballots have been returned statewide. Of those, 16,602 were from either Milwaukee or Dane counties, or about 1 in 3 statewide. By comparison, in the heavily Republican suburban Milwaukee counties of Waukesha, Ozaukee and Washington, only 4,589 early votes have been cast.

Milwaukee and Madison began offering in-person absentee voting on Sept. 26 after a federal judge ruled in July that a two-week limit on voting early was unconstitutional. Other smaller cities, towns and villages have also been allowing voters to cast ballots weeks ahead of the election. Still others will begin or expand early voting opportunities in the next three weeks.

Clinton's and Feingold's campaigns have been making a push in recent days for early voting in Wisconsin, with Vermont Sen. Bernie Sanders and Massachusetts Sen. Elizabeth Warren coming to the state for get-out-the-vote drives. Feingold appeared with Sanders on Wednesday and he planned to attend a downtown Madison rally with Warren on Friday.

Trump and Feingold's opponent, Republican Sen. Ron Johnson, have also been encouraging their supporters to get to the polls early. Trump scheduled a campaign stop Saturday in southeast Wisconsin, where he will be joined by Johnson, House Speaker Paul Ryan, Gov. Scott Walker and other Republican officeholders and top officials.

Early voting opportunities vary across the state. Green Bay, where people lined up to cast ballots in the April presidential primary and there is an open congressional seat, has only one location for early voting open at the city clerk's office downtown. That has generated complaints from Democrats who want early voting to also be available on the University of Wisconsin campus about 5 miles away.

City clerk Kris Teske has said she doesn't have the staff or budget to expand hours and locations.

Liberal advocacy group One Wisconsin Now has pushed for expanding early voting in Green Bay and other cities, including Kenosha and Racine. Scot Ross, director of the group, said it was "unfortunate" that early voting hours and locations are so haphazard across the state.

"Everybody should have as long of a period to vote as possible," Ross said.

Madison and Milwaukee plan on expanded early voting locations. Milwaukee has had just one voting location since Sept. 26, but two more sites open Monday. Eleven polling places are open in and around Madison, with three to open later in October at the University of Wisconsin and Edgewood College.

Neil Albrecht, Milwaukee elections commissioner, said he wasn't surprised that the first 10 days of early in-person voting resulted in only about 3,200 ballots cast in his city. In 2012, when early voting was limited to three weeks before the election, about 36,500 people in Milwaukee voted that way. Albrecht said he anticipated those numbers to be at least 20 percent higher by the time early voting ends on Nov. 5, three days before the election.

In Madison, about 4,800 people had voted in-person absentee by Thursday morning. County clerk Scott McDonell said he expected the numbers to exceed 2012 levels as more people vote closer to Election Day.

A breakdown of how many were mailed-in versus cast in person was to be released Friday. In 2012, more than 512,000 people cast in-person absentee ballots statewide in the presidential race out of about 659,000 absentee ballots in total.