It's judgment day for two of the longest-serving members of Congress, both of whom are fighting for their political lives.

The contests involving Republican Sen. Thad Cochran of Mississippi and Democratic Rep. Charlie Rangel of New York -- who have each served more than four decades on Capitol Hill -- are the marquee matchups Tuesday as seven states from the East Coast to the Mountain West hold primaries.

Also in the spotlight: a high-profile tea party vs. establishment Republican contest in the GOP Senate primary in Oklahoma; the Republican gubernatorial primary in Colorado, where a controversial and outspoken former congressman is one of the frontrunners; and the GOP lieutenant governor's runoff in South Carolina, where a 2014 contest may have 2016 implications.

Here are five contests to watch on this busy primary day:

1. Bitter battle in Mississippi: Take a six-term Republican senator fighting for another six years in Congress and a tea party-backed state senator who's challenging him. Mix in nasty attacks on both sides, a bizarre incident involving the incumbent's nursing home-bound wife, tons of cash by outside groups and lots of big names from the world of politics and even sports and entertainment parachuting onto the campaign trail, and you've got the GOP Senate primary runoff in Mississippi.

State Sen. Chris McDaniel narrowly edged out Cochran in the primary three weeks ago, but with neither man cracking 50% (there was a third Republican candidate on the ballot who grabbed 1.5% of the vote), the contest moved on to a runoff.

Cochran, who's touting his seniority in the Senate and his ability bring in the federal bucks, is backed by much of the state's GOP establishment, many national Republicans and outside groups such as the U.S. Chamber of Commerce, which traditionally supports mainstream Republicans. His backers argue a McDaniel victory in the primary could put a very safe GOP seat in play in November's general election.

But tea party groups and anti-establishment Republicans see Cochran as the problem, and his comments back in February, when told reporters that "the tea party is something I don't really know a lot about," didn't do him any favors.

Several tea party and anti-establishment groups have run ads backing McDaniel or helped with get-out-the-vote efforts in support of the candidate.

In the runoff campaign's closing days, big names parachuted into the state. Former Sen. Rick Santorum, a 2012 GOP presidential candidate who may run again in 2016, campaigned with McDaniel, and Sen. John McCain of Arizona, the 2008 Republican presidential nominee, hit the trail in support of Cochran.

But wait, there's more: The race also turned into a battle of celebrities.

Longtime game show host Chuck Woolery -- famous for hosting "The Dating Game" and "Love Connection" -- headlined a bus tour organized by the Tea Party Express in support of McDaniel. Woolery's appearance came just a couple of days after pro football great Brett Favre, a Mississippi native, starred in a U.S. Chamber of Commerce TV ad for Cochran.

McDaniel's supporters say House Majority Leader Eric Cantor's defeat two weeks ago in his primary in Virginia to a little-known and underfunded tea party candidate is giving the challenger's supporters even more energy. The big question is whether Cochran can expand the electorate by persuading black Democrats to come out and vote for him.

2. Rangel's last run: Win or lose, Rep. Charlie Rangel of New York says this is his last campaign. The Korean War veteran, who was first elected to the House of Representatives 44 years ago, is trying keep from getting pushed out office by his main primary challenger, state Sen. Adriano Espaillat, who came within around 1,100 votes of ousting Rangel in the Democratic primary two years ago.

Rangel, the former chairman of the powerful tax-writing Ways and Means Committee, was forced to step down from his post in 2010 and later that year he was censured by the House for ethics violations.

Just as damaging for Rangel was the redrawing of New York's 13th Congressional District after the 2010 election, from a Harlem-based, African-American-dominated district to one that now has a Hispanic majority, thanks to shedding parts of Harlem and adding other neighborhoods in northern Manhattan and parts of the Bronx.

Rangel, one of the best-known politicians in the country, remains confident.

"If you had a race horse that won 43 races, brings in the money, but the horse is old and experienced and knows the track -- what would you do?" the 84-year-old Rangel asked reporters this past weekend. "Would you send him to the glue factory? Hell no."

Espaillat says Rangel is emblematic of all that ills Congress.

"This is a coalition of victory that is completely convinced that Washington is broken and that at the center of that dysfunction is a gentleman called Charles Rangel," he said Saturday.

Rangel's confidence was buoyed by a nonpartisan poll last week that indicated he held a 13-point lead over Espaillat, who if elected in November would become the first member of Congress born in the Dominican Republic.

But some political analysts say it's difficult to poll in the district and feel the race is much closer. Plus, Rangel suffered the embarrassment of failing to win endorsements from President Barack Obama and New York City Mayor Bill de Blasio.

"If Rangel were he to be defeated, it would be a huge national story, but not a shocking one like Eric Cantor's loss, since Rangel barely escaped defeat two years ago," Lee Miringoff, director of the Marist Institute for Public Opinion, told CNN.

3. A run to the right in Oklahoma: Sen. Tom Coburn's announcement in January that he would step down at the end of the year -- with two years left in his term -- sparked a competitive primary to replace the conservative senator. There are seven candidates in the race, but the contest is really a battle between the two frontrunners: Rep. James Lankford and former state House Speaker T.W. Shannon.

For a party looking for more diversity, the 36-year old Shannon, who was the youngest speaker ever of the Oklahoma House, is an attractive choice. He's part Native American and African-American. He's been backed by such tea party heroes as Sen. Ted Cruz of Texas and former Alaska Gov. Sarah Palin. And some national anti-establishment organizations have pumped big bucks into the race in support of Shannon.