The debates are over, the speeches are winding down, even the TV commercials should taper off -- at least, for now. Voters Tuesday will cast ballots to elect a U.S. senator for the next six years -- or to narrow the field to two for a Dec. 6 runoff. Here’s a look at the election by the numbers.

8 — That’s how many candidates appear on the U.S. Senate ballot for the Tuesday open primary. Two are current members of Congress: Mary Landrieu, the Democratic incumbent; and U.S. Rep. Bill Cassidy, of Baton Rouge, her best-financed Republican challenger. A second Republican -- retired Air Force Col. Rob Maness, of Madisonville -- is making his first try for elective office, and is the only other candidate to mount a legitimate statewide campaign.

50 + 1 — That’s 50 percent of the vote Tuesday, plus one more vote -- the minimum that any one candidate needs to win election outright Tuesday. If no candidate equals or betters that mark, then the top two finishers meet in a Dec. 6 runoff. Opinion polls consistently show that Landrieu and Cassidy will top the field, but that both will fall short of a majority and will go at it again Dec. 6.

2,935,143 — The total of registered voters in the state. How many of them actually participate in the election will play a major role in determining the outcome. A high voter turnout generally favors Democrats, because several of their traditional supporter groups -- minorities, younger voters, lower-income voters -- don’t vote as reliably as other groups that favor Republicans.

45 - 50 — Percentage of voters that Louisiana Secretary of State Tom Schedler estimates will participate Tuesday, based on historical patterns for elections for Congress that don’t coincide with presidential elections. In 2010 -- a non-presidential year, with the state’s other U.S. Senate seat atop the ballot -- fewer than half of the state’s voters turned out. In each of the last two presidential elections, in 2008 and 2012, more than two-thirds voted.

30/30 — The Landrieu campaign’s “magic number” for success. Landrieu can win, her campaign says, if black voters -- who give her near-unanimous support -- account for 30 percent of the electorate Tuesday (they make up 31 percent of all registered voters) and she also gets 30 percent of the white vote. The numbers can vary a bit from that so long as they add up to 60.

6 — Republicans need to pick up at least six seats in the Senate this fall to capture a majority there and add that to their existing House majority, which would increase their ability to put political pressure on Democratic President Barack Obama and set the stage for the election of the next president in 2016. As an incumbent Democrat in a state that has voted for Republicans in all statewide elections since her last win, in 2008, Landrieu is a prime target of the Republican effort. Others on the Republican hit list are Democratic incumbents in Alaska, Arkansas, New Hampshire and North Carolina, plus the open seats now held by Democrats in Montana, South Dakota and West Virginia. Democrats hope to dump Republicans from Senate seats Republicans now hold in Georgia, Kansas and Kentucky.

30.4 million — Total amount, in dollars, of money raised by the campaigns of Landrieu ($16.8 million), Cassidy ($11 million) and Maness ($2.6 million), making this the most expensive Senate election in Louisiana history (based on federal filings through Sept. 30). No other candidate on the ballot has raised as much as $10,000. In addition, outside political groups have spent additional millions on advertising attacking or supporting the candidates.

38 — Obama’s approval rating in Louisiana, in the percentage of voters favoring him in a recent University of New Orleans poll. His national approval rating isn’t much better, and Republicans in Louisiana and other states have tried to tie Democratic Senate candidates to the unpopular president.

97 — The percentage of the time Landrieu votes with Obama’s position in the Senate, according to Cassidy. Cassidy has repeated that number over and over in a campaign focused on Landrieu’s collaboration with Obama -- who, Democrats point out, will leave office two years into the six-year Senate term.

18 — Years Landrieu has served in the Senate. Because of her seniority, she took over early this year as chair of the Senate Energy and Natural Resources Committee, with oversight of the oil and gas industry that is central to Louisiana’s economy. Landrieu has heavily promoted the “clout” she has acquired in the Senate and can employ of behalf of her state’s interests. Republicans say she can’t use her leverage effectively so long as her party, with its national anti-energy agenda, controls the Senate.