Missouri Gov. Jay Nixon, right, has been a ubiquitous figure as tornadoes and flooding ravaged his state over the past two months. And his response could help insulate the Democrat from President Obama’s poor numbers in his state. (AP Photo/Jeff Roberson, File)

Many of the top governor’s races of 2012 will also be held in key presidential swing states, but if the last two elections are any guide, the voters in these states are happy to split their ticket between the presidency and the governor’s mansion.

In 2008, there was at least a ten-point variance between the governor’s race and the presidential contest in 10 of the 11 states hosting both; in six of the states, the variance between the two races was more than 20 points.

In 2004, with President Bush running for reelection, the results were at least 10 points different in seven of 11 states.

In both 2004 and 2008, four of those 11 states split their vote, picking a Republican for one office and a Democrat for the other.

North Carolina, Montana, Missouri and New Hampshire all loom as potentially competitive gubernatorial and presidential contests in 2012. But more often than not in those states, the result in the governor’s race has been far different than the presidential.

In Montana in 2008, Gov. Brian Schweitzer (D) won reelection by 33 points, even as Obama lost the state by three points. The same year, Missouri Gov. Jay Nixon (D) won his first term by 19 points while Obama narrowly lost the state, and New Hampshire Gov. John Lynch (D) won by 42 points as Obama won the state by nine.

In 2004, former North Carolina Gov. Mike Easley (D) won reelection by 13 points as Democratic presidential candidate John Kerry (Mass.) lost the presidential race in the state by 12. And when Schweitzer won his first term by four points, Kerry lost by 20.

Now, there have been cases where the two results have been closely linked. Obama has been credited with delivering current North Carolina Gov. Bev Perdue (D) a victory in 2008, as both won the state narrowly. The same could be said for former Missouri Gov. Matt Blunt (R) and Lynch when they first won their seats in 2004. All three of those races tracked very closely to the presidential race results in their respective states.

The cases in which the presidential candidate does matter to the gubernatorial race tend to be open-seat contest in which both sides put forward a formidable candidate.

As for 2012, Perdue and Nixon are running for reelection, so they could be insulated from any negative Obama top-of-the-ticket effects.

Perdue is less popular than Obama in her state, while Nixon is more popular. It’s hard to see Obama winning North Carolina and bringing Perdue across the finish line unless her numbers significantly improve. By the same token, Nixon is looking more and more like a favorite in a state where Obama’s team may struggle to compete.

There is an open seat in Montana, where the field is in flux, and there’s no word yet on whether Lynch will seek a fifth two-year term (though many expect he won’t) in New Hampshire.

So if you’re looking for states where Obama could matter to the gubernatorial outcome, keep an eye on Montana and New Hampshire. Across the rest of the country, the governor’s races aren’t likely to be heavily affected.

Our look at the top five governor’s race likely to switch parties between now and 2012 are below. As always, the number one ranked race is considered the most likely to switch.

To the Line!

5. Missouri (Democratic-controlled, 2012): Nixon’s solid response to the tornado in Joplin, Mo., last month solidified the picture of a popular incumbent who will be tough to beat. Lt. Gov. Peter Kinder (R), meanwhile, has stumbled out of the gate. About the only thing that suggests Kinder has a chance is the presidential race. (Obama lost the state in 2008 and isn’t likely to win in 2012.) But as we discussed above, that may not be worth much. If Lynch retires in New Hampshire, this one may fall off the list soon. (Previous ranking: 4)

4. Kentucky (D-2011): On paper, Kentucky should be a prime Republican pickup opportunity. But races aren’t won on paper, and candidates matter. That’s Republicans’ problem. State Senate President David Williams has proven to be a weak candidate to date, while Gov. Steve Beshear (D) has made few mistakes. Recent fundraising numbers tell the story; Beshear had $2.7 million to spend on the fall campaign, while Williams had just $89,000. The conservative tilt of the state has and will continue to keep Williams in the game, but he needs to put together a much stronger effort in the coming months to oust the incumbent. And Beshear hasn’t given people much reason to send him packing. (Previous ranking: 2)

3. Washington (D-2012): Gov. Christine Gregoire’s (D) decision not to seek a third term wasn’t at all surprising and likely gives her party a better chance to hold the seat next November. Both parties appear to be rallying behind a single candidate — for Republicans state Attorney General Rob McKenna, for Democrats Rep. Jay Inslee (who will officially enter the race next week). Given Washington state’s Democratic lean, Inslee starts off as a slight favorite, but Republicans have been waiting for years for the well-regarded McKenna to run for the top job and believe he has a real chance at pulling the upset. (Previous ranking: 5)

2. Montana (D-2012): We are still waiting for state Attorney General Steve Bullock (D) to pull the trigger. If he does, this is a competitive race and Democrats may even have a slight edge; if he doesn’t, it may be the most likely Republican takeover of the bunch. But Democratic sources still expect him to get in the race. The one saving grace for Democrats as they wait for Bullock is that the GOP field is still unsettled and features no big names (though state Senate Majority Leader Jeff Essmann is considering tossing his name in the mix and would likely jump to the head of the line). Lt. Gov. John Bohlinger (R) is also weighing his options, but it’s not clear which primary he would run in or that he’s inclined to run at all. While a Republican, he has twice been the running mate of a Democratic governor (Schweitzer) and doesn’t seem convinced he can win a GOP primary. (Previous ranking: 3)

1. North Carolina (D-2012): Former Charlotte mayor Pat McCrory (R) is moving closer to declaring a rematch with Perdue, signaling the start of what will be a very hard-fought race. He held a fundraiser this week and has started attacking Perdue and Obama. Polling suggests Perdue has made some gains in recent weeks, and every time she has vetoed a bill from the Republican-controlled legislature, her numbers go up. (She just vetoed a GOP budget along with a Voter ID bill, so we’ll see if that continues). It remains to be seen whether Perdue is in the midst of a comeback or simply experiencing a temporary bump. (Previous ranking: 1)

Chris Cillizza and Rachel Weiner contributed to this report.