It all starts in Pennsylvania.
Here's a breakdown:

April 22
Pennsylvania (158)

Make no mistake about it - Pennsylvania has an importance that no one could have possibly anticipated. Not only is it the first contest in six weeks, but there will also be a two-week gap following the Penna. primary.  So there will be plenty of time to digest and regurgitate every possible angle of the vote.

What was once viewed as a last line of defense for Hillary Clinton is rapidly becoming a potential crisis for the Obama campaign.  The demographics, the economics, the geopolitics all favor Clinton.  She has the endorsements of most of Pennsylvania's super delegate officials.  She had a 10% lead in many polls as recently as a month ago. Then the poll numbers became to close.  However, the timing of Senator Obama's "bitter" rural voters comment could not have been worse.  Combined with the lingering aftershocks of the Rev. Wright disclosures, this may have a devastating impact on Obama in the voting booth.

Pennsylvania's primary is closed - only registered Democrats are allowed to vote.  In nationwide polls, Clinton tends to do better among self-identified Democrats while Obama does better with independents.   However, Clinton and Obam have split closed primaries to date.  Democratic registrations surged before the deadline in March - to 4.2 million, 1 million more than the Republicans.  The Obama campaign was deeply involved in new registrations in the state. Whether those new voters flip the lever for Obama remains to be seen.

If Clinton loses the nomination is over. Period. If Clinton wins by only small single digits, she will have a difficult time making her case.  But if she wins by more than 10%, it will put the Obama campaign on the defensive.  More than 15% will be a bombshell.  I believe that all of the above factors point to a large Clinton victory in Pennsylvania.   And from such a victory much of the following is likely to transpire.

May 3
Guam (3)

Guam is not on the map.
Its three caucus delegates will likely go 2/1 Obama.
This may be the best news Obama receives all month.

May 6

Indiana (66)
North Carolina (91)

Indiana is not Illinois. Just like Alabama is not Georgia or New Hampshire isn't Massachusetts. But more so.  Alabama and Georgia have had similar presidential voting trends for decades, not so Indiana and Illinois.  For many Hoosiers, even if they go up to Chicago to visit, shop, and watch a Cubs game, Chicago is the great "other".   Outside of Indianapolis and Gary much of  Indiana is like downstate Illinois culturally - small-town, agricultural - precisely those areas addressed by Obama's "bitter" comments.   Indiana also has a small African American population - 7.8% - half that of Illinois.  The Pennsylvania results will have an impact on Indiana voters.  The combination of strong showing by Clinton in Ohio and Penna. will energize Clinton supporters and dissuade a significant portion of independents who might have voted for Obama in February.   Clinton is likely to win Indiana by 10%

North Carolina will be a firewall for Obama - much as Texas and Ohio were for Clinton in early March.  But the poll numbers may belie different vote totals when the counting is complete.  There has not been a primary since the Rev. Wright story broke and Obama used the term "bitter" to describe rural people.  North Carolina is one of the most churched states and still significantly rural / small town.   In addition, despite hopeful numbers early on, Harvey Gantt always ended up with fewer votes against Jesse Helms than predicted.  African Americans do constitute roughly 40% of registered Democrats; however, the primary is open to independents, as well.  Since the Republican primary is moot, the preponderance of independents, most of whom are white, will vote in the Democratic primary, likely reducing the black proportion of the Democratic primary vote to about 25%.  Given the size of the Pennsylvania defeat that Obama might have and given the degree of news coverage of that defeat, Obama may well struggle to pull out a win in North Carolina.  If Obama wins by only small single digits he will be seen as on the ropes.

May 13
West Virginia (26)
There will be big news from West Virginia on May 13th.  Obama will lose badly in the primary, possibly by as much as 20%; yet, he will have scored impressively in the county conventions held in April.  What in April appeared a boon to Obama will rebound against him. News outlets will not only report the disparity between Democratic operatives at he county conventions vs. the primary results, but they will also extend this to earlier Obama caucus wins as part of a larger discussion of caucuses and primaries.   By this point, Obama will have lost primaries to Clinton in Ohio, Texas, Pennsylvania, Indiana, and West Virginia. He will have won only the two tiny caucuses, Wyoming and Guam, and two Southern primaries, Mississippi and North Carolina.

May 20
Kentucky (47)
Oregon (48)

Kentucky is a foregone conclusion.  After big Obama defeats in Indiana and West Virginia, this could be a landslide for Clinton.  Kentucky's importance wil be that it is another state in a long list of recent Obama losses - big losses.  It will also offset the results from Oregon.

Speaking of Oregon, the primary results in Oregon are not certain by any means.  Even though Oregon is not Washington, the Washington results are informative.  Washington held both caucuses and a "beauty contest" primary.  Although Obama won the caucuses by a huge margin - 68% to 31% - he only barely won the primary - 51% to 46%.  The Washington primary was open to independents. The Oregon primary is closed - only for registered Democrats. Given Obama's pattern of greater support among independents this may suggest a closer race in Oregon.  In addition, the polls of Washington showed a significant tightening in the last week, even at a time when Obama was at his peak nationally.  Thus, the Oregon primary could be a toss-up. And if Clinton wins, it will be a devastating loss for Obama.

June 1
Puerto Rico (55)

Another stunning defeat for Obama.  Since Puerto Ricans cannot vote in November, there should be a huge turn-out.  The Obama campaign would be wise not to disparage Puerto Rican voters given Obama's poor showing among Hispanics.  Another big loss in a string of losses for Obama.

June 3
Montana (15)
South Dakota (14)

By June, the pattern will be quite clear.  Not only has Obama failed to close the deal, he will be struggling for survival.  Montana is an open primary - its super delegates are split; however, the big guns, Baucus, Schweitzer, and Tester, remain uncommitted.  South Dakota is a closed primary - its super delegates have largely endorsed Obama, albeit in February.  Given the string of Obama losses, given Obama's comments about rural people and those of his former minister, given the fact that these Western states are holding primaries, not caucuses - it seems highly likely that the results will favor Hillary Clinton, perhaps not by much, but enough for her to win.

Later in June ?????
Florida (185)
Michigan (128)

If Clinton defeats Obama in the vast majority of late primaries, there will be a renewed call for revotes in Florida and Michigan.  Why?  The Democratic super delegates will need as much evidence as possible to choose someone other than Barack Obama. But one thing is for certain - if Obama loses these primaries, the super delegates will deny him the nomination. The revotes in Florida and Michigan will simply be political cover - sad to say. All evidence points to a significant Clinton lead in Florida - which will be overwhelming in June if Hillary is sweeping the table.  Clinton will also likely carry any Michigan revote if she has already won Ohio, Penna., and Indiana.