Coverage of the race for the Senate has, rightfully and unsurprisingly given the seats in play this cycle, focused on the 23 Democratic-held Senate seats being contested this fall, as opposed to the 10 Republican-held seats. With so many targets, Republicans have many opportunities to go on offense, with seemingly few places to play defense.

But there are some warning signs for Republicans, and GOP leadership might remember some advice that Admiral Greer (James Earl Jones) gave Jack Ryan (Harrison Ford) in the classic Clear and Present Danger: “Watch your back, Jack.”

Indeed, even if Republicans can pick up some Democratic-held seats, their chances at a Senate majority could falter if they lose a seat or two where they’re currently favored.

The candidates matter

Part of the Republicans’ problem is a common one in this anti-establishment era: candidate selection. Primary results have already turned one super safe seat — Indiana — into a potentially competitive one, and might affect other seats where primaries are still pending. Conservative icon William F. Buckley’s advice to Republicans was to vote for the most conservative candidate who can win. As Republicans found out two years ago, ignoring those last three words can lead to trouble.

Primary victories by Tea Partiers arguably cost the Republican Party a shot at a 50-50 U.S. Senate in the 2010 elections. Sharron Angle (NV), Ken Buck (CO) and Christine O’Donnell (DE) all defied the odds to win their primaries, only to lose to vulnerable Democrats in November.

The same anti-establishment, pro-outsider sentiment that fueled Republicans in 2010 remains vibrant, and outsiders are continuing to win Republican Senate primaries. Their victories may or may not end up benefiting Democrats in the fall.

While Tea Party/anti-establishment challengers have hardly swept this year’s Senate primary battles — Sen. Orrin Hatch (UT), ex-Rep. Heather Wilson (NM) and ex-Sen. George Allen (VA) are notable “establishment” primary victors — the outsiders have notched some memorable victories. Chief among those is Indiana Treasurer Richard Mourdock, who defeated Sen. Richard Lugar, and state Sen. Deb Fischer, who came out of nowhere to defeat two better-known opponents in Nebraska.

Fischer looks like an easy winner against ex-Sen. Bob Kerrey (D). But Mourdock’s victory turned another reelection waltz by Lugar into a potentially hotly contested race in Indiana. While the Hoosier State has swung back to the GOP after narrowly supporting President Obama in 2008, one cannot completely discount Rep. Joe Donnelly’s (D) chances of winning an upset. If he does, it will be because of Mourdock’s primary win.

Meanwhile, in toss-up Wisconsin, a multi-candidate field makes Badger-land’s Republican primary hard to predict. Ex-Gov. Tommy Thompson appears to be the leader — while polling is all over the map, the Marquette University Law School Poll (which basically nailed the result of the Wisconsin gubernatorial recall) still puts Thompson up in the primary and general — but he faces strong opposition from self-funding businessman Eric Hovde and Club for Growth-backed ex-Rep Mark Neumann. (Assembly Speaker Jeff Fitzgerald is the forgotten man in this race at the moment.) Thompson, distrusted in some conservative quarters because of his past support for the individual mandate included in the Affordable Care Act, polls best against presumptive Democratic nominee Rep. Tammy Baldwin, and he would start out as the favorite in the race if he wins the primary. That said, Hovde might be the next Sen. Ron Johnson (R), an outsider businessman who beat Sen. Russ Feingold (D) in 2010.

Another seat that bears watching is in Republican-leaning Arizona, where Democrats love their candidate — former Bush administration Surgeon General Richard Carmona — and the GOP has an unexpectedly hot primary brewing between Rep. Jeff Flake and outsider, self-funding businessman Wil Cardon. Flake recently called in the big guns, getting endorsements from Arizona Republican Sens. John McCain and Jon Kyl (whose retirement has opened up this seat). Flake also has the support of the Club for Growth, which is generally known for backing insurgents, but not in this instance. Yet Arizona Republicans might not think that Flake is sufficiently hard-line on immigration, and Cardon has boatloads of money to spend.

Against Flake, Carmona’s a competitive underdog; against Cardon, it could very well be a toss-up race.

In Indiana, the results of the primary made a safe seat competitive; in Arizona and Wisconsin, the primary results might bolster GOP hopes — or endanger them.

One other primary of note: It appears that insurgent Ted Cruz could knock off Lt. Gov. David Dewhurst in the Texas Senate primary. This race has no bearing on the battle for the Senate — the seat is safely Republican no matter the outcome of the runoff — but it’s another data point in the insider/outsider primary dynamic on the GOP side, with a potential Cruz win meaning another victory for the outsiders.

The general election: 94 down, six to go?

We have only one rating change to announce in this Senate update, but it is a notable one: We’re moving Sen. Dean Heller (R-NV) from toss-up to leans Republican. The recent flare-up in the ethical investigation into Rep. Shelley Berkley (D) forced our hands. Obviously, this is one that could still flip to the Democrats if Obama does well in the Silver State, and wily Sen. Harry Reid (D) and his political machine must never be underestimated. But Heller has to be considered the favorite at this point.

That rating change allows us to present a rather tidy general election picture: if every senator not up for reelection returns to the Senate at the start of 2013, and every race safe, likely or leaning to one party or the other stays that way, the Senate would be 47-47, with one party or the other needing four of the six toss-ups to guarantee itself control.

Descriptions of those six toss-up races follow, along with our sense of which side may have the advantage at this point. We emphasize the last three words because we’re not ready to call these races, only describe the mid-summer drift.

Florida: Sen. Bill Nelson (D) consistently leads polling against Rep. Connie Mack, his likely Republican challenger. Mack’s unsteady and overly sensitive performance has drawn a late Republican primary challenger, ex-Rep. Dave Weldon, but Weldon doesn’t appear to have the financial strength or name recognition to compete. Mack’s father won this Senate seat in 1988 thanks to a big lift from George H.W. Bush at the top of the ticket; his son may not need Bush’s 61% presidential performance in 1988 (a margin that Mitt Romney won’t come close to matching), but given that Nelson should run at least a point or two ahead of Obama, Mack will need some coattails to win. ADVANTAGE: NELSON

Massachusetts: Democrat Elizabeth Warren, despite the bad headlines generated by her supposed Native American ancestry, continues to raise money at an incredible pace: $8.6 million just in the second quarter. Sen. Scott Brown (R) is no fundraising slouch either — he raised $5 million — but he may need more help to fend off Warren and President Obama’s coattails in this deeply Democratic state. It seemed as though the Warren controversy would be that help, but it hasn’t changed the numbers at all. ADVANTAGE: WARREN

Missouri: There’s so much Republican primary drama across the nation that we didn’t even get the chance to mention the three-way battle in the Show Me State among businessman John Brunner, Rep. Todd Akin and ex-Treasurer Sarah Steelman. One would think that the businessman, Brunner, would be the “outsider,” but national Republicans seem to prefer Brunner to the other two candidates. Sen. Claire McCaskill (D) awaits the winner, and this may be, to borrow a sports term, a race between the movable force and the resistible object: a weak challenger going against a struggling incumbent. Given the way the political winds are blowing in Missouri, McCaskill’s probably in trouble no matter what. ADVANTAGE: GOP primary winner

Montana: Incumbent Sen. Jon Tester (D) is winning plaudits for winning a strong campaign, and he’s also besting opponent Rep. Denny Rehberg (R) in fundraising. But Montana, like Missouri, should not be all that close at the presidential level, meaning that Tester needs to keep up the good performances and fundraising to hang with Rehberg. Given the polarization this year, it won’t be easy. ADVANTAGE: REHBERG

Virginia: The winner of the Old Dominion might very well win the presidency, and the winner of its Senate seat might control the upper chamber. The race between ex-Gov. Tim Kaine (D) and ex-Sen. George Allen (R) has been in stasis for more than a year, and both sides are sticking to their respective strategies: Allen, banking on an Obama loss in Virginia, is tying the ex-Democratic National Committee chairman to his president, and Kaine is doubling down on his support for Obama by appearing with him during a recent campaign swing. So far Obama is a slight favorite in toss-up Virginia, and given that we’ve yet to meet an Obama-Allen swing voter, you would think that Kaine would also be a tiny favorite in the toss-up Senate race as well. But we are being cautious on our own state, and we are not yet convinced that the critical, narrow Obama lead will hold. Let’s revisit this one after the two national party conventions have concluded. ADVANTAGE: NONE

Wisconsin: As noted above, if Tommy Thompson wins the primary, he would start as the favorite (as in, we could see moving this race to leans Republican). But if any of the others win, the race stays a toss-up, and might even tilt to Tammy Baldwin. ADVANTAGE: NONE


Drilling down on the Senate toss-ups shows that, in the race to 51 seats, it remains either side’s race to win — or to lose, which is where these remaining Republican primary battles might make a difference. We also suspect that an autumn drift in the presidential race, driven by economic reality, will reset a few Senate races and change our current outlook.

It’s also worth remembering that some of the states we list as leaning Democratic — Hawaii, New Mexico and Ohio — might end up going to Republicans in the right fall climate. So might some of the leans Republican seats, such as the aforementioned races in Arizona and Indiana and, in particular, the surprisingly close contest between Rep. Rick Berg (R) and ex-state Attorney General Heidi Heitkamp (D) in North Dakota.

But in many ways, the race for the Senate hasn’t really changed much since late February, when Sen. Olympia Snowe (R-ME) announced her retirement. That probably handed a seat to the Democrats — in the form of independent ex-Gov. Angus King — and locked the race for the Senate into a coin flip battle where the coin, when tossed on Election Day, might land on its side, in the form of a 50-50 Senate. That would require the vice president, whoever that is, to tip the coin one way or the other.

To see our full list of Senate ratings and candidates, click here.