There are more tea party vs. establishment primaries tonight.

Politico notes that if Sen. Pat Roberts (R-KS) and Sen. Lamar Alexander (R-TN) win today, “this will be the first cycle since 2008 in which no incumbent senator loses in a primary.”

Harry Enten says Alexander and Roberts “are heavy favorites to win their primaries this week against conservative challengers, but the data from past primary challenges suggest that Alexander has a higher chance of being upset.”

Roll Call has 6 things to watch as results come in.

“She is such a dominant frontrunner. I think most people will decide to stand down.”

— David Plouffe, quoted by the Wall Street Journal, on Hillary Clinton’s presidential chances.

New York Times: “They aim to match President Obama’s feat in 2012, when the incumbent used topics such as same-sex marriage and contraception as weapons to offset his vulnerability on the economy. That they would even try while facing the older, whiter, more conservative midterm electorate shows how thoroughly the politics of social issues have turned upside down.”

“The tumultuous social changes that began in the 1960s supplied decades of political ammunition for Republicans. Beginning with Richard M. Nixon, they rallied Americans disturbed by noisy protests over civil rights, the sexual revolution and the Vietnam War.”

“With the prospect of a Republican takeover of the Senate looming, the White House is quietly mulling potential silver linings of such a dynamic during President Obama’s final two years in office,” the Wall Street Journal reports.

“While it’s hard to find anyone in the administration who sees any upside for Mr. Obama if the GOP controls both chambers of Congress-certainly no one is making a public case-one optimistic view of a GOP-controlled Congress is that maybe Mr. Obama would finally be able to cut some deals.”

“The idea is that after November, Republicans will be less inclined to block Mr. Obama because they’ll be looking toward the presidency in 2016 and will want to round out the GOP record to include some planks that have broader national appeal; at the same time, Mr. Obama could have more space to make deals because Democratic leaders won’t be reining him in with their own congressional politics.”

Chris McDaniel (R) has formally challenged his defeat in a runoff by Sen. Thad Cochran (R-MS) in Mississippi, the Jackson Clarion Ledger reports.

“McDaniel will have to prove there were enough illegally cast votes to change the outcome or that the election was so sloppily handled its result is in doubt.”

McDaniel claims 3,500 of illegal crossover voting by Democrats, 9,500 “irregular votes” and 2,275 “improperly cast” votes. Certified results show Cochran won by 7,667 votes, or 51 percent.

Rick Hasen: “But the reason I expect McDaniel will likely lose is that he is not asking for a new election. Instead, he is asking for a remedy of having him declared the winner.”

“If he chose to run, he would be the most creditable candidate for president since Henry Clay.”

— Sen. Mitch McConnell (R-KY), quoted by the Huffington Post, likening Sen. Rand Paul (R-KY) to another famous Kentucky politician.

Nate Cohn: “Republican hopes for attracting more Hispanic voters suffered another setback on Friday when the House passed a bill to effectively end President Obama’s program to defer deportations of undocumented children. Yet the vote is unlikely to deal a severe blow to the party’s chances in November’s midterm elections. Hispanic voters may be flexing their growing political muscles in presidential elections, but they have far less sway over the composition of the House or the Senate, particularly in 2014.”

“Barack Obama has been a disaster. I guess that’s what we get for electing someone with no experience. He was only two years into his first big job when he started campaigning for the next one. Sound familiar?”

— Sen. Mitch McConnell (R-KY), quoted by Politico, campaigning against challenger Allison Lundergran Grimes.

Nate Silver: “The problem for Democrats is that this year’s Senate races aren’t being fought in neutral territory… It therefore shouldn’t be surprising that we continue to see Republicans as slightly more likely than not to win a net of six seats this November and control of the Senate. A lot of it is simply reversion to the mean.2 This may not be a “wave” election as 2010 was, but Republicans don’t need a wave to take over the Senate.”

“Summing the probabilities of each race yields an estimate of 51 seats for Republicans. That makes them very slight favorites — perhaps somewhere in the neighborhood of 60-40 — to take control of the Senate, but also doesn’t leave them much room for error.”

“However, I also want to advance a cautionary note. It’s still early, and we should not rule out the possibility that one party could win most or all of the competitive races.”

The Upshot says Republicans have a 53% chance of winning control.

A new Human Events/Gravis Marketing poll in Wisconsin finds Gov. Scott Walker (R) and challenger Mary Burke (D) deadlocked in the race for governor, 47% to 47%, with 6% still unsure.