5 Things to Know for Tuesday's Missouri primary

   A look at various issues and facts affecting your primary election day in Missouri:

   COME INFORMED, BUT DRESS LIGHT.

   1. Polls in Missouri will be open from 6 a.m. until 7 p.m. Tuesday, with about 25 percent of Missouri's registered voters expected to cast ballots. If you're going to vote in the middle of the day, dress comfortably: the heat wave that's gripped Missouri will persist with forecast highs in the mid- to upper 90s across most of the state.

   2. MISSOURI'S HOTTEST RACE: U.S. SENATE.

   On a crowded Missouri ballot, one race towers above all: the hotly contested three-way race among Republicans for the right to challenge incumbent Democratic U.S. Sen. Claire McCaskill. Congressman Todd Akin, businessman John Brunner and former Missouri Treasurer Sarah Steelman have been busy establishing their conservative bona fides. Each has significant support: Akin is endorsed by former presidential candidate Mike Huckabee, Steelman is backed by former vice presidential nominee Sarah Palin and Brunner is supported by the U.S. Chamber of Commerce.

   3. FROM TWO, ONE.

   Though many congressional districts feature contested primaries, few have grabbed as much attention as the 1st District, where incumbent William Lacy Clay Jr. will face 3rd District Rep. Russ Carnahan. The unusual battle came about after Missouri's Legislature was faced with reducing the state's nine congressional districts to eight following the 2010 Census. The cut came in heavily-Democratic St. Louis, and Carnahan's former 3rd District was wiped off the map -- forcing Tuesday's showdown.

   4. KINDER FIGHTS FOR HIS POLITICAL LIFE

   Perhaps the most personally combative race rests with the GOP primary for lieutenant governor. Incumbent Republican Peter Kinder and state Sen. Brad Lager have traded sharp personal and political barbs. Lager has sought to seize on Kinder's personal and political gaffes, including his visits to a St. Louis-area strip club while serving as a state senator in the 1990s. Kinder claims Lager personally profited from the health overhaul through his job at a health care technology company.

   5. EXPANDING THE CONSTITUTION'S LANGUAGE ON PRAYER

   Voters will also decide whether to expand an existing section of the Missouri Constitution to state that people can pray in public if they do not disturb the peace, and that a prayer is allowed before government meetings. It would state that students cannot be compelled to participate in school assignments or educational presentations violating their religious beliefs. Supporters contend the language reinforces the right to pray and protects students, while opponents say it could cause confusion over what is allowed and is likely to trigger lawsuits.