Sen. Thad Cochran (R-Miss.) is the underdog in a runoff with state Sen. Chris McDaniel, and could end up the first Senate incumbent to lose this year. Rep. Charles Rangel (D-N.Y.) faces his toughest reelection challenge yet as he seeks a 23rd term. And Rep. James Lankford (R-Okla.) is trying to fend off a tea party-backed former state House speaker in the race for an open Oklahoma Senate seat. Colorado and Maryland also are holding primaries.

Wins by the candidates running as outsiders could feed into an anti-Washington narrative that was given life when Cantor, the House majority leader, lost in Virginia two weeks ago. But if the men already in Congress stay put, it could make Cantor’s loss look like an outlier.

( Full primary election results here)

Here are six questions that will be answered as results come in:

1. Will non-Republicans show up to save Thad Cochran in Mississippi?

McDaniel, 41, received slightly more votes in the primary than Cochran, the 76-year-old seeking a seventh term. Turnout usually drops in a runoff, which in this case would give an edge to the more motivated, more conservative activists who are backing McDaniel.

Cochran and super PACs supporting him are trying to mobilize African-Americans, moderate suburban women and other nontraditional primary voters to cast ballots for the incumbent. Democrats are allowed to vote in the runoff if they did not cast ballots in the state’s June 3 primary, but counting on them is a tall order and risks a backlash on the right.

The Senate Conservatives Fund, one of McDaniel’s biggest backers, is spearheading a “voter integrity project” to place volunteer observers in polling places to make sure that Democrats who voted in their party’s primary don’t vote in the GOP runoff. Cochran allies suggest this amounts to voter intimidation.

( Also on POLITICO: ‘The Brad Pitt of the Republican Party’)

The state’s political establishment has pulled out all the stops for Cochran. The current governor, Phil Bryant, and former Sen. Trent Lott, once a rival, both cut ads, as did football legend Brett Favre. Cochran’s camp has used clips from his old talk radio show to paint McDaniel as a misogynist who could lose to Democrat Travis Childers in a general election.

In a reflection of how this race has become a proxy battle in the larger Republican civil war, Sen. John McCain flew down to campaign for Cochran while his 2008 running mate Sarah Palin stumped with McDaniel. If Cochran loses, this will be the third consecutive cycle that a Republican senator has lost a primary.

( Also on POLITICO: The Cochran-McDaniel ad wars)

2. Are the Baptists more organized than the tribes in Oklahoma?

The special Sooner State primary to replace retiring Sen. Tom Coburn would have received a lot more national attention if Mississippi had not gone to a runoff.

Before being elected to the House in 2010, Rep. James Lankford, 46, ran the biggest Baptist summer camp in the state for a decade and a half. He has strong backing from the religious right. T.W. Shannon, the African-American former speaker of the statehouse, is a member of the Chickasaw Nation, whose gambling interests make it a major player in Oklahoma politics.

( Earlier on POLITICO: Coburn rips outside right groups)

The tribes have money to spend, but the Baptists have the organizational muscle to turn out the vote.

Polls have shown a tight race, although a survey released Monday by SoonerPoll.com put Lankford up 8 points. If neither man breaks 50 percent, the runoff is Aug. 26. The winner faces no credible Democratic opposition.

3. Does Charles Rangel survivein New York?

The 84-year-old legendary Harlem politician barely won his Democratic primary in 2012 against state Sen. Adriano Espaillat, and now, as he faces a rematch, Rangel is taking nothing for granted — campaigning intensely at every step.

But the demographics in Rangel’s district have changed, becoming more Hispanic and less African-American, and a cloud still hangs over the former Ways and Means Committee chairman because of a 2010 ethics censure.

( DRIVING THE DAY: Primary preview)

Gov. Andrew Cuomo’s late endorsement Sunday reflects the growing conventional wisdom that Rangel will win, and the last independent poll showed him up 13 points. But pollsters warn the district is notoriously tough to survey, and others in New York City’s political establishment have declined to endorse in the race, as has President Barack Obama.

If Rangel goes down, Democrats are guaranteed to hold the seat, but it will be the end of an era in Harlem politics.

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4. Will Tom Tancredo hurt Republican Senate hopes in Colorado?

There’s a four-way Republican primary to challenge Democratic Gov. John Hickenlooper, and national Republican strategists fear Tom Tancredo will emerge as the GOP nominee.

Tancredo, 68, is the former congressman who sought the Republican presidential nomination in 2008, then unsuccessfully ran for governor as a third-party candidate in 2010.

In a general election, Tancredo’s very conservative positions on a host of issues — but especially against illegal immigration — could galvanize Democratic base voters who are otherwise unlikely to show up without Obama on the ballot.

A Democratic-linked group, Protect Colorado Values, has spent half a million dollars trying to boost Tancredo in the primary and damage his main rival, former Rep. Bob Beauprez. Also running in the primary are former state Senate Minority Leader Mike Kopp and Colorado Secretary of State Scott Gessler.

An outside group called Republicans Who Want to Win has run an ad saying Democrats prefer to run against Tancredo. Another group, called Make Colorado Great Again, has spent $150,000 on an ad that accuses Tancredo of wanting to decriminalize drugs.

The sense is that the race is way too close to call, but there’s been scant public polling. In part because Hickenlooper is seen as less beatable than a year ago, one concern is that Tancredo will benefit from low turnout.

5. Do GOP establishment favorites win in three key New York House races?

Republican Rep. Richard Hanna faces a spirited primary challenge upstate from Assemblywoman Claudia Tenney, who is attacking the congressman over his support for gay marriage.

The 22nd District incumbent has gotten backup from major GOP donors, such as Paul Singer, but Tenney is getting help from social conservative groups. All-but-announced 2016 presidential candidate Rick Santorum, for example, recorded a last-minute robocall supporting Tenney for Citizens United.

Two of the best opportunities for House Republicans come in Empire State districts, where there are contentious primaries between retreads and fresh faces favored by D.C. strategists.

In the 21st District, a reddish upstate area, Democratic Rep. Bill Owens is retiring. Self-funder Matt Doheny, who narrowly lost to him in 2010 and 2012, is trying a third time. But Elise Stefanik, a young GOP operative who grew up in the district, has received public support from the likes of Mitt Romney, Paul Ryan and American Crossroads, which has spent hundreds of thousands of dollars attacking Doheny.

In the 1st District, on Long Island, Democratic Rep. Tim Bishop won by fewer than 2,000 votes in 2012.

In the GOP primary to face him, state Sen. Lee Zeldin has support from the U.S. Chamber of Commerce and other establishment groups. But George Demos, a self-funder, has the backing of former New York City Mayor Rudy Giuliani and former Gov. George Pataki. National Republicans prefer Zeldin over Demos, who lost in the 2010 GOP primary.

6. What is Anthony Brown’s margin in the Democratic primary for Maryland governor?

Outgoing Gov. Martin O’Malley’s lieutenant governor leads by 20-plus points in the final polls from The Baltimore Sun and The Washington Post.

Brown, an African-American veteran, is well positioned to trounce Maryland Attorney General Doug Gansler and Heather Mizeur, an openly gay state delegate running as an unabashed liberal. But the race could tighten if turnout is low.

As O’Malley gears up for a potential presidential run — the Democrat was in Iowa over the weekend — the primary is a referendum of sorts on how his base sees him in his home state.

O’Malley campaigned with Brown on the eve of the primary, but their administration has taken heat over the disastrous rollout of an Obamacare exchange and their push to raise taxes during the past eight years. Whoever wins the deep-blue state’s primary will be heavily favored to prevail over whichever of the four Republicans emerges from the GOP primary.