This is a strong Republican ticket against a strong Democratic ticket. Historically, there are headwinds against the party that held the White House for two terms. I would imagine Hillary's numbers go down even further when she's a partisan presidential candidate. However, Christie's tone might not be as effective when he's running against an elderly woman with a presidential resume.
Categorizing states...
Really Safe D: Washington DC, Hawaii, Vermont, New York, Rhode Island, Maryland, Delaware, Massachusetts (77 EV)
Safe D: California (55 EV)
Likely D: Connecticut, Illinois, Washington (39 EV)
Lean D: Oregon, Maine, Minnesota, Michigan (37 EV)
Democratic-leaning tossup: New Mexico, New Jersey, Colorado, New Hampshire, Virginia, Wisconsin, Nevada (73 EV)
Republican-leaning tossup: Ohio, Pennsylvania, Iowa, Florida (73 EV)
Lean R: North Carolina, Indiana (26 EV)
Likely R: Nebraska's liberal district, Missouri, Arizona, Georgia, Montana (39 EV)
Rather Safe R: Texas, Louisiana, Alaska, Mississippi, South Carolina, Most of Nebraska, Arkansas (74 EV)
Really Safe R: Utah, Wyoming, Oklahoma, Idaho, West Virginia, Kentucky, Alabama, Kansas, Tennessee, North Dakota, South Dakota (65 electoral votes)
Half the time, Christie would win with 279 electoral votes. This would be a 50/48 popular vote split.
If it's a good cycle for the Republicans, he'll do better. A 340 win is doable with the right headwinds.
But Clinton probably has a 33% or so chance of winning nicely with 303 electoral votes, if the popular vote goes 50-48 in her favor.