Congressman Bill Cassidy spent Monday knocking on doors in the Baton Rouge subdivision where he grew up.

Three-term U.S. Sen. Mary Landrieu rallied union members in Baton Rouge and Rob Maness ate ice cream in the north Louisiana.

All three major candidates for the U.S. Senate spent a frantic Monday looking for just enough support to win Tuesday’s election outright; an outcome few think is likely.

Polls will be open from 6 a.m. to 8 p.m. Tuesday. State government is closed, as are most public schools. But many private and parochial schools will be open.

Because of the possible role Louisiana may play in deciding which party controls the Senate, voters could see national and international news media at the polls monitoring the election.

The Senate race may be the headliner, but voters across Louisiana are choosing all six representatives to the U.S. House and deciding 14 amendments to the state constitution.

Voters in Lafayette, Acadia and Vermilion parishes will decide whether to give District Attorney Mike Harson another six-year term or replace him with Keith Stutes, a former veteran prosecutor in the 15th Judicial District.

Stutes has been hitting the incumbent hard over a federal bribery investigation that has ensnared three of Harson’s former employees, each pleading guilty to putting DWI defendants into diversion programs in exchange for gifts and cash. Harson, who was not implicated in the investigation, has touted his work with schools and creation of pretrial diversion programs that give offenders a second chance.

Within the criminal justice system, voters also will decide on Lafayette’s city marshal, two seats on the 15th Judicial District Court and a city judge for Lafayette.

Lafayette voters will weigh in on the School Board, where for the first time in years all nine seats are contested. A total of 20 candidates are vying for a seat on the board, including six incumbents. In recent months, the board has been largely consumed by an ongoing struggle with Superintendent Pat Cooper over his leadership of the school system — a subject certainly discussed during the election. But candidates, too, debated overcrowded schools, aging facilities, teacher morale and whether they supported charter schools.

There are also municipal elections in Broussard, Youngsville, Scott, Carencro and Duson, though incumbent mayors in Broussard, Carencro and Scott and a new mayor in Youngsville won without opposition after no one qualified to run against them. In Carencro, the entire leadership of the city was re-elected by default — mayor, police chief and five-member council.

Also in Acadiana, U.S. Rep. Charles Boustany, R-Lafayette, faces nominal opposition in his re-election bid for the 3rd Congressional District.

A much more competitive race is expected in the 6th Congressional District. Former Gov. Edwin W. Edwards, 87, faces 10 other candidates in the hotly contested race. The 6th District covers much of southeast Baton Rouge and its suburbs, down to the western suburbs of New Orleans and over into Houma.

Edwards, as the best-known of the three Democrats running in an overwhelmingly Republican district, is expected to find enough votes to make the Dec. 6 runoff.

It’s a tight race among the seven Republicans, four of whom have raised significant funds and show up neck and neck on various polls. They are state Sen. Dan Claitor; Garret Graves, the top coastal adviser in the Jindal administration; and Paul Dietzel, a 28-year-old entrepreneur, all from Baton Rouge, as well as state Rep. Lenar Whitney, from Houma.

In the headliner Senate contest, Landrieu pushes the clout she has accumulated over the past 18 years. She is chairwoman of the Senate committee that oversees energy policy. Republican Cassidy claims unseating the Democrat will lead to a new era that will roll back the programs of President Barack Obama. Maness, a Republican running to the right of Cassidy, promises more conservative values in government.

Though Landrieu and the Democrats are pushing for an outright win Tuesday, the more likely scenario is a Dec. 6 runoff, probably with Cassidy, if the polls are to be believed.

Hanging over the race from a national perspective is whether the Republicans will win control of the U.S. Senate, as they have in the U.S. House. The GOP needs to pick six seats to make a majority in the upper chamber of Congress and have targeted incumbent Democrats, like Landrieu, who were elected from states dominated by Republicans.

Handicappers said Monday that the GOP takeover was likely, with The Washington Post giving that outcome a 7 in 10 chance.

In another closely watched contest, incumbent U.S. Rep. Vance McAllister’s easy ride to re-election in the 5th Congressional District became bumpy when he was caught kissing a married aide.

He had run as a “family values” candidate and won the seat last year with the support of Monroe Mayor Jamie Mayo and the Robertson family who star in “Duck Dynasty,” the reality show on cable television.

This fall, however, Mayo is running as the only Democrat and the Robertsons are backing Republican Zach Dasher, of Calhoun, a nephew of patriarch Phil Robertson, who says this time the candidate “has been vetted” by the family.

Other Republicans in the race include Dr. Ralph Abraham, of Mangham; Harris Brown, of Monroe; Ed Tarpley, of Alexandria; and Louisiana Public Service Commissioner Clyde Holloway, of Forest Hill.

The 5th District covers northeast and central Louisiana along with parts of the Florida parishes along the Mississippi border.

Secretary of State Tom Schedler calculates 52 to 53 percent of the state’s 2.9 million voters will turnout Tuesday. That’s more than the 44.2 percent in 2010, the last midterm election, which swept Republicans into control of the U.S. House, but less than the 67.9 percent in 2012, when President Barack Obama ran for his second term.

“I hope for 60 percent. But quite frankly the data just doesn’t tell me that,” Schedler said.

About 1.3 million voters in 4,018 precincts will use about 10,000 voting machines to cast ballots Tuesday.

Each machine can handle about 20 voters an hour, he said.

“There are going to be lines,” Schedler said. “It’s one of the longest ballots we’ve seen.”

At 8 p.m. sharp, precinct officials will mark the end of the line and allow those people still waiting, to cast a ballot.

“We may not finish voting until 8:30, maybe quarter to nine,” Schedler said, saying that the outcomes in tighter races may not be known until well after midnight.

Follow Mark Ballard on Twitter @MarkBallardCNB. For more coverage of government and politics, follow our Politics Blog at http://blogs.theadvocate.com/politicsblog/