This race is going to be interesting to watch.  Too interesting for those heavily vested in one candidate or the other.  Travis Childers is the type of Dem who can pull this off.  But Davis has advantages as well.  A look:

Childers advantages:
-The Chancery network.  This courthouse connection across district is the reason we're talking about him and not Steve Holland right now.
-Image.  Childers has a mild demeanor, comes across as your friendly neighbor.  This will play well in the rural counties.
-Locale.  By geography, Childers is going to know people on the east side of the district or people who do.  And this could garner him a few votes that might go to Pubs normally.
-Unity.  Dems are as united as Dems can be and Pubs are less so (but not as bad as the media are portraying).
-Turnout.  Dems are generally more motivated to vote this year.  Whether that carries over to a Special election (3rd in less than 2 mos.) is something nobody knows.

Childers disadvantages:
-He will not come off as sophisticated to some people.  The Dem party is these days a coalition of the super-rich and super-educated and the poor and low-educated.  The "super" end of that crowd generally prefer someone who seems a little more elitist or more of a fad.  Granted, this is MS and not a national race, though.
-The 1D is a natural Pub district.  Less natural than the 3D, but still is natural lean to that party.
-Crossovers.  How many Pubs crossed over to vote Dem on March 11?  A bunch.  How many of them chose to vote in the Dem runoff since they were locked in?  Not sure. But at least some of those Dem voters are Pubs and may "come home" on April 22.
-Money.  Childers was third in money in Runoff (behind McCullough and Davis).  He obviously doesn't have a donor network.  This will improve now that he's the nominee, but it's still a disadvantage.  And much of that improvement will come from out-of-state and national Dem sources.  That type of influence will not play well in rural Miss.  Once Childers starts taking that money, he becomes less of a local neighbor and more of somebody tied to Pelosi, Dean, et al.

Davis advantages:
-He's the Pub nominee in a Pub district.  For Nov. at least, he benefits from the McCain, Wicker and Cochran efforts to help with turnout, etc.  They will run as a ticket sorta and should.  Gov. Barbour, Phil Bryant, et al, will also be strong behind Davis.
-Money.  While struggling to raise money against McCullough by comparison, this will now get easier.  He'll be able to diversify his message through the airwaves better.
-Desoto.  Desoto county and its spinoff in Tate and Marshall contain a goldmine of votes that will go Pub.  These voters have to be turned out to have power, but Davis has demonstrated he can do that (McCullough wouldn't have been able to pull this off 3 weeks after beating up on the hometown favorite).  In Childers's home base, there's maybe 6,000 votes.  Davis has 10 times that easily in his.
-Record.  Davis has a strong record on everything from values to military to economic development, etc.  As a mayor and legislator, he's had opportunities to have to speak and work on these issues and has done well.  Childers as Chancer Clerk has simply not had such opportunities.  Records are good indicators of what to expect from somebody and Childers (through no fault of his own) just doesn't have this.

Davis disadvantages:
-Party unity.  This isn't as much of a problem as it's being played though.  Outside the Lee County area, the party has already lined up behind Davis (I'm not sure about Lowndes).  So, he's already unified it quite nicely already.  He has to work on Lee County though and has began that process.  It's hard so soon after Runoff, but there's no choice.  However, in private circles it's known that McCullough was unpopular even among his supporters.  Most of his Lee County support was due to one of 3 factors:  1)Respect for his father, Cotton and their family; 2) Locality/familiarity/Connection.  Devil you know vs. devil you don't know.  3) A little fear of McCullough if he got in and they didnt' support him.  The media missed this and it's why the party will unite easier than is being realized.  McCullough could help this with an endorsement, but it will happen regardless.
-Name ID on east side of district.  McCullough lacked name ID in Desoto, but Davis lacked it more in NE Miss.  This has improved, but due to the runoff's negative tone, it's not all good.  Childers will attempt to define Davis negatively by painting Davis as negative vs. the positive Childers.

Prediction:  Not really ready for that yet, but lean towards decent odds for a runoff and a May 13 election (uggh!).  Like most elections, it will depend on turnout.  Will Dems remain motivated in this Groundhog Day election?  Will Davis be able to get Desoto to pump out 3 times in 9 weeks?  Will McCullough supporters and party regulars work enough to show up for Davis and secure the seat?  Too close to call on all accounts right now.  Let's see how the advertising and fundraising go over next 10 days and it will be easier to see.  If I had a gun to my head, I'd say Childers in April and Davis in November, though.  Thankfully, I don't have a gun to my head and can just say "I don't know".